Bottom line. I think the GH4 will be technically better but the Sony will be more fun to use.
I'm not a fan boy of anything, so cameras work better for me than others and like I said if the Sony hit all the points I need I'd go that way . . . if the file "looked" cinema like.
Personally, I think all motion cameras should have a super 35mm or something close format, just because it's a standard, you can think in those numbers rather than a 14 is a 28 X .3.
I understand the technical reasons but that doesn't mean I like them, though it won't stop me from buying two gh4's, because the 3's opened up our lifestyle work like no camera ever has.
Though for me and this isn't to compare against the Sony, I know the gh3's I use are really as you say fun, because they work in a form factor I'm used to and with practice autofocus like nobody's business.
When I get my gh4's I'll test them, but would bet that I use them as 2k 10 bit 422 cameras more than I'll ever use 4k,due to the 200 mbs data transfer, but that's just a guess because they aren't out yet.
I do have to give credit to all the companies that are coming out with these smaller form factor cameras. I simply love my olympus omd's for stills, can't imagine not having them and am quite use to the 2x crop.
This simple little still shot was with an em-1 at 1250 of a second F 2 or less, with very scrimmed down 575 hmi. I also shot the same image with my Leica s2 and of course the depth of that file far outstipped the olympus, but the olympus was sharper in movement due to shutter speed and shoots very pretty.
I'm not knocking Sony but I think they disappoint when it comes to their lower end cameras. There is always a gotcha and I've never understood it because I doubt if any company has the technical ability of Sony, no company seems to intentionally hold back like Sony does.
Sony's a7 cameras aren't a new idea, but a good idea, though I'd love to see them not knee jerk. Olympus has a hit with a retro style omd and Sony tries a one up on the A7(R), then panasonic announces a good priced 10 bit 422 4k and Sony announces 4k, though with less specs.