It is hard to tell someone what to buy. The quality of the image and video from the LX100 is very good to excellent. Is it as good as the GH4? I would say if you are a pro and looking for the equal of the GH4 then the answer is no.
But if you are an enthusiast and can cut the camera some slack, you would be hard pressed to tell the difference.
Remember, I have only had the LX100 here for about 5 hours now, so as time goes on my opinion may change.
The disappointing thing about the LX100 is it is certainly not a baby GH4. The camera is 80 percent a point and shoot camera that dips into the higher end here and there. The menus try and emulate the GH4, but they are clumsy, and not just a little bit clumsy - low end pint and shoot type camera clumsy. I am quite surprised.
The camera would be a deal breaker for me if it were not for the really good quality video. I expect the images to be excellent too, it leans in that direction but I won't know until I can shoot RAW.
Here is a simple example. Say you are not totally or only a video guy. Video is really high on your list, but you want to take meaningful pictures too. I am a photographer, so when I take pictures - even just home pictures - if they are not "excellent" you know darn well the comment "and you are supposed to be a photographer" is going to hit you head on. To achieve those excellent pictures consistently, you really have to have control of the camera. So, take the LX100 in hand, go to take a shot and you will notice you have no control over the focus point. You can press 3 buttons and get control, or set the menu so you can have direct access to the 4 way controller just like the big boy cameras :) As you shoot along you want to do a custom white balance (something a lot of folks won't ever do) and you find you no longer can do a custom white balance unless you go into the menu and undo your setting to have direct access to the 4 way controller dial. You can change the white balance, but you can't do a custom white balance.
Now go to video.Is the quality as good as my GH4? not quite. But at 4K reduced to 1080, it is head and shoulders better than any direct 1080p camera I have used. Again, no custom white balance unless you go and reset the main menu back to the way it was. So now you give up using the 4 way controller easily and just go thru the hoops.
Bottom line, coming down fro the GH4 the feeling is yuck. Coming up from a Canon G1X II or a Sony RX100-3, the camera is terrific.
I won't be grabbing the LX100 for any pro level work, images or video. But I think most people will like the LX100. Its calling card is the 4k video quality - especially when going down to 1080 - and the bigger sensor for all other imaging. The focus is quite good and the camera surpasses almost all other point and shoot sized camera I have used. My problem is at $900 i would really really wanted more of a nod to having some usable features in it. For stills I cannot select a "lowest shutter speed" like I can on the EM1, but the GH4 doesn't have that either.
The GH4 with a 12-35 is a dream. It just works - period. if you do put the size differences in the mix, then get the 12-35 lens. If you want a 12-35 lens (almost, but not quite) and a free camera thrown in, then get the LX100.