I rank the Sound Devices MixPre 3/6 above the Zoom F4/F8 for pure sound quality: smoother, fuller, more natural sounding, more analog like, and of course the amazing analog limiters. I base this on owning a Zoom F4 and a Sound Devices USB Pre2 (which has the same audio topology as the 744T, meaning it sounds as good as the higher end SD recorders) as well as the YouTube/SoundCloud comparison videos: Couldn't find any comparisons of Sound Devices to Zaxcom, Nagr