I own neither of these cameras, so I don’t actually know
However, were I to choose to buy the top of the range camera, it would under any and all conditions be the GH3. Why? Because I place great value on video, and because I do not shoot JPEG.
Back to my article … so why do these two criteria (video, JPEG) tip the balance? And how do I even know that these are real differences? Well, the video one is easy … but for confirmation, you can look at Thom Hogan’s article on the all-round winner of the best serious camera of the year.
Thom is an accomplished reviewer with a very strong technical background in engineering and imaging, so you should listen to him before you listen to me, obviously :-)
All-round … has a nice ring to it. But it also means that things that do not matter to an individual shooter are factored in. So my personal choice factors those out and the GH3 ends up stomping the OM-D.
A relevant quote from Thom illustrates this perfectly … this is from the section that documents why the runners up are the runners up :-) … and it is for the GH3:
My GH3 came late in the year, so I'm still ferreting out it's image quality. My initial impression is E-M5 like raw, but Panasonic still hasn't quite gotten their JPEG rendering up to Olympus levels. That's actually one of the things that made me decide against the GH3 as the potential winner: it's a beast for video, but doesn't establish that same clear advantage in basic still shooting. If you are seriously thinking about getting the E-M5, I think you have to look at the GH3. I'll bet that size, video, and JPEG quality are the three things that tip you one direction or the other.
So let’s look at these three criteria:
Size: Yes, this will matter if you want just one camera body and it has to do a bit of everything. But I have four bodies already and they are all small enough. Two are smaller than an OM-D and I carry one of these whenever I go out. The GH3 would be the biggest of them all (one body to rule them all?) but that would not be why I bought it.
Video: I’ve had a long-running argument with a raging fan boy on dpreview.com regarding the video of the OM-D … he likes to use passive aggressive questions to try to bully me into giving him a shopping list of reasons why the GH3 is better than the OM-D, when in fact there are so many sites that discuss it as to render it an axiom. But just to be complete, let’s take another quote from Thom’s treatment of the GH3:
Panasonic GH3 — If this were the "Best Video in a Mirrorless Camera" awards, the GH3 would not only take that award, but it would slap the others silly as it did so. The bare specs don't tell the full story, but the GH3 is a powerhouse when it comes to video. Power. House. Indeed, short of recording uncompressed HDMI off the Nikon DSLRs, I believe it to be the only DSLR-like still camera that can output broadcast quality video streams (50Mbps+; the Panasonic can do 72Mbps).
And a further note: I can hack three of my four bodies to output broadcast quality video (hopefully, Vitaly will do the G5 later on.) That’s a Panny thing; the Oly equivalent is pure jello on all bodies except for the OM-D, which does not suck the way the others do. In fact it has one lurking advantage in that it can stabilize your primes properly. So if that is your primary criteria … hand held video with primes … then the OM-D is your camera. But for me, the Panny advantage is clear and obvious. Period.
JPEG Quality: Bzzzzt! Thank you for playing. I don’t care. At. All.
So … for me, it is a no-brainer. Were I handing out awards, the GH3 would be the winner as serious camera of the year. Because in 2012 and 2013 video matters!
Kim’s irrelevant and under-researched award for serious camera of the year goes to: all the Panasonic m4/3 bodies :-) Seriously, you really cannot go far wrong with any of the modern m4/3 bodies, especially those shooting a 16mp sensor.
Anyway, that’s just my take in a puff piece where I have handled the OM-D only once and have never even seen a GH3 in the wild … but I can read and do some pattern matching of what people are saying and with great ease I can formulate my own thoughts on the matter :-)
Whichever one you buy, enjoy it. Both are great cams. And so are the GH2, the G5, the G3, the GX1 and so on …. (E-PL5 and E-PM2 also for stills, but not that good for video.) Even the GF3 is pretty excellent in most circumstances … Thom even gave the newer GF5 top honors as the entry camera of the year in mirrorless.