If you're looking for a new full-frame camera from Canon, you've got some options now that the new Canon 6D is beginning to ship. We've already seen some samples from that camera, but it's hard to know how it compares to the other models without looking at all of them directly. Mitch from planet5D has gotten a hold of the Mark II, Mark III, and 6D simultaneously to see if the new model still exhibits some of the same issues that the Canon 5D Mark III has fixed.
It's clear that the 6D is not going to best the 5D Mark III. Canon made sure that was the flagship of these cameras, and it's still the best-looking camera under the 1D X, which is debatably a little sharper, possibly at the cost of letting in a bit more false color. If you've been using the Mark II forever and you haven't run into anything that has bothered you considerably, I don't think the 6D will be much different. The 6D has other considerations that make it a better camera than the Mark II, like the HDMI output, the internal recording codec, etc., so all of these things would be upgrades for anyone who has been hindered by those in the past.
It may be disappointing to some that the 6D won't be as good as the Mark III, but it's clear they've put most of their energy into a few select models and will basically recycle video into the other cameras as they see fit. I would be fine shooting with the 6D, as I loved the Mark II except for the little quirks that have been improved upon (though we're still missing the headphone port). If you're not trying to shoot a lot of detailed wide shots, most of the problems you see above will be out of focus in the background. That's not to say you'll never see them, but this test was specifically designed to break the cameras, and while the Mark III came out on top, it's also $1,000 more expensive. For some people, that may be too much for a dual purpose camera, so it's good that you can weigh your options among all three models.
Johnnie Behiri, who shot some of the previous test footage, added a clip to his beta test of the 6D, and I've embedded that below. I think it's a good counterpoint to the footage above -- instead of breaking the camera, it is attempting to make the camera look as good as possible at higher ISOs (800 and 1250) with 30% post sharpening and a little bit of color correction:
What did you think of the 6D? How did it compare for you to the other cameras? What did you think of it in the second clip, does that change your mind at all?