Don Kotlos

I dont know  what your problem is BUT he is a 1Dx ii user who had the A7iii 'for about a week'. It is almost certainly littered with 'new toy' exaggerations although he did at least vlog with the camera..
But the Op here asked for opinions. And I dont know who is better to give opinions than someone who has used both cameras. Admittedly a week isnt a long time but it is fairly long in terms of the A7iii when the camera was only released in the US two weeks ago.
If you happen to be better qualified to give your opinions go ahead....

IMHO the new generation of Sony cameras A7III/A7rIII/A9 are significantly better than their predecessors in every way possible. So I would suggest people keep their mind open and avoid propagating false information unless they have direct experience. 
That being said, the experience at least when shooting pictures is very different between a DSLR and a mirrorless. I still find the OVF a pleasure to use but only when there is enough light. When things become a bit darker the EVF is far ahead. Tracking should be faster in the 1DXii, but if you shoot prortraits/people then the Eye/Face detect is very useful. The other advantage of any mirrorless is shooting with the LCD which is still clunky with most DSLRs. 
On the video side, sure the AF of the 1Dxmkii will be better but the newer Sonys are actually very close. The IBIS is the major factor that drove me to mirrorless really. Having the ability to stabilize any lens makes shooting so much more enjoyable as well. I also find the colors of the new Sony cameras very good. To my eye after you play around a bit with the settings they can definitely be better than Olympus/Nikon/Panasonic. 
If you have the money, I would suggest to rent on for few days. You might like it or hate it and it can save you quite a bit of money in the long run. 

Other than the imminent release of A7sIII ? 
Joking aside, it seems the only real downside is the excessive noise reduction at higher ISOs with gammas different than slog as illustrated in the video that @Simon Young posted. 
Other than that I believe you will be very satisfied. 

There is one dial at the front. Since I didn't spot anything in the menus, I am guessing for the time being it is just for the aperture. 

I respectfully disagree about the video quality being better on the a7iii than the riii. I’ve used both extensively and I agree about the a7iii being maybe one stop better in low light and more detailed in full frame, but there’s something about the image of the riii in full frame that’s simply more pleasing, even if you get the occasional moire and aliasing artifacts. Maybe it’s got something to do with the riii having less rolling shutter or being a tad “softer”, thus resulting in a more organic image.
I also feel the build quality and evf (obviously) being a notch above the a7iii. Is the Riii worth the price though? Highly questionable for 99% of potential buyers who are more video oriented.
And what about those ghosting artifacts? They are nowhere near as severe in the a7riii due to possibly better nr algorithm. (Read Arturs description).

Dialogue in Panasonic headquarters meeting:
(Manager) Well, Cinelike-D and Cinelike-V should stay available only for our bigger body cameras...
(Engineer) Ahn...there is a problem...
(Manager) What?
(Engineer) A guy in a site was messing with our wifi transmission protocol and discovered a way to enable it in our smaller cameras.
(Manager) Oh, fuck. Where?
(Engineer) Looks like a Canon site by their name, EOSHD. @BTM_Pix is the handle of the guy.
(Manager) Can't we disable it with a firmware update?
(Engineer) We can...but since we usually only release updates to fix errors in our smaller cameras, and not to improve them like that Fujifilm assholes, probably will not be a good idea.
(Manager) How did that happened?
(Engineer) An internship guy was assigned to handle the wifi protocols and...
(Manager) Amazing job, geniuses. Now we have to enable it to not look selfish...

The engineer was moved to Panasonic's washer division.

=================================================================
 
New firmware v1.1
[Cinelike D] and [Cinelike V] have been added to [Photo Style].
[Flash Mode] can now be set to [Forced Flash Off] for the built-in flash.


http://av.jpn.support.panasonic.com/support/global/cs/dsc/download/fts/dl/gx9.html

I just found a Q&A with a 'Black Magic Design Expert'. Let me know if there's a better way to display this. I'll try to add to it as more information comes.
















 

In my opinion with cameras that have baked-in sharpening & contrast, the sharpest, cleanest, most flare-resistant lenses, usually give the worst results.  

My best guess is that he was smoking something while making assertions like this: 
"IMO, The Gh5 (even before the "s" model, SMOKES the C500." 
 

Of course.  This is obviously just a quick way to get a basic understanding so one can make an informed choice.

Don, I think News/ENG camera ops are the real ones living in their own universe still. Zooming, focusing, riding the iris without thinking twice about it. Just experience and muscle memory for these people. Heavy rigged cameras, beefy sticks and head etc, and they do it solo, day in day out.
Attached a photo of an old timer in OZ shooting digital for the first time in his life, no drama to get around a problem.

In my opinion with cameras that have baked-in sharpening & contrast, the sharpest, cleanest, most flare-resistant lenses, usually give the worst results.  

In my opinion with cameras that have baked-in sharpening & contrast, the sharpest, cleanest, most flare-resistant lenses, usually give the worst results.  

In my opinion with cameras that have baked-in sharpening & contrast, the sharpest, cleanest, most flare-resistant lenses, usually give the worst results.  

Here is another unique use of ML
https://petapixel.com/2018/04/10/this-short-film-was-shot-at-2520mm/
 

It is highly unlikely for the A7sIII to have any form of 10bit. At least internal.  They would need to use a different wrapper other than the XAVC-S for that. Also it would undercut the FS5ii. XAVC-S can support 4K 60p though so I am confident we will see that. 
If they manage to get the fast readout times of their stacked CMOS sensor with video and offer near global shutter performance, coupled with 4K 60p, excellent low light, battery performance and very good AF that would still be an excellent camera and a worthy update from the A7sII. If the use the 24MP sensor of A9 then that would make it even better since hybrid shooters will appreciate the extra resolution for photos. 
While I would like 10bit as much as any other member of this forum, Sony does not have that much competition yet in order to potentially sacrifice sales of their professional line. Someone could argue that GH5/s is a good alternative but once you have the 60p with near global shutter and very good AF with a 24mp FF sensor it would distance itself by quite a bit. And I really doubt Nikon/Canon would come up with a FF mirrorless camera and internal 10bit anytime soon. 
That brings me back to the FS5II. A reason that Sony only updated a firmware might be because the competition is still slow. All C200/EVA1/FS5II have some form of RAW, 4K 60p, low light that is not that different. C200 offers a vastly better AF than the other two, EVA1 has the highest resolution sensor and FS5II has the electronic ND. Maybe color was the only thing Sony needed to address in order to match the competition...

My best guess is that he was smoking something while making assertions like this: 
"IMO, The Gh5 (even before the "s" model, SMOKES the C500." 
 

The pics are not even from the test. 
They are from a corporate videographers gh5, who claims the gh5 "smokes" the C500.  And for him it probably does. Less weight, hassle ect...
If you are interested in facts here you are. 
www.alfonsoparra.com/images/articulos/investigacion/digital_nohd/pdf/c500_en.pdf. 
For those that don't read:
12 stops for the c500 @ 10 bit.  11.68 for the gh5s "test"   We won't mention bit depth, actual resolution, raw, etc...
 

It is highly unlikely for the A7sIII to have any form of 10bit. At least internal.  They would need to use a different wrapper other than the XAVC-S for that. Also it would undercut the FS5ii. XAVC-S can support 4K 60p though so I am confident we will see that. 
If they manage to get the fast readout times of their stacked CMOS sensor with video and offer near global shutter performance, coupled with 4K 60p, excellent low light, battery performance and very good AF that would still be an excellent camera and a worthy update from the A7sII. If the use the 24MP sensor of A9 then that would make it even better since hybrid shooters will appreciate the extra resolution for photos. 
While I would like 10bit as much as any other member of this forum, Sony does not have that much competition yet in order to potentially sacrifice sales of their professional line. Someone could argue that GH5/s is a good alternative but once you have the 60p with near global shutter and very good AF with a 24mp FF sensor it would distance itself by quite a bit. And I really doubt Nikon/Canon would come up with a FF mirrorless camera and internal 10bit anytime soon. 
That brings me back to the FS5II. A reason that Sony only updated a firmware might be because the competition is still slow. All C200/EVA1/FS5II have some form of RAW, 4K 60p, low light that is not that different. C200 offers a vastly better AF than the other two, EVA1 has the highest resolution sensor and FS5II has the electronic ND. Maybe color was the only thing Sony needed to address in order to match the competition...

Com'on Jon, use the Vehydra 12mm at f/5.6 and and anything that you can follow will be in focus  

Which is something that I and plenty of other people find obscene. No company should have a say with what I do on something that I have bought. Or how I want to upgrade my computer that is.
https://www.bleepingcomputer.com/news/government/eu-prepares-right-to-repair-legislation-to-fight-short-product-lifespans/
https://www.bleepingcomputer.com/news/government/us-states-considering-legislation-to-introduce-right-to-repair-for-electronics/
https://www.bleepingcomputer.com/news/government/ftc-warranty-void-if-removed-stickers-are-illegal/
"Limiting repair options illegal under 1975 US law
The FTC says that such practices are illegal under the Magnuson-Moss Warranty Act, a law that governs consumer product warranties, and which states that no company can put restrictions on the way users choose to repair their products.
The law says that companies can't force users to use only certain types of (astronomically-priced) replacement parts, take produces for repair jobs only at certain repair shops, or can't plaster anti-tampering stickers on products to prevent users from repairing their own products."

Ha! Are you referencing the fact that content originally mastered in 2k is regularly upscaled and then released as 4k?  I'm  curious about the physical format, not necessarily the content.