This morning Canon announced the EOS 6D, a low cost full frame camera that will no doubt fit into the same price bracket of the recently announced Nikon D600. The question is, how do they compare? Without having a opportunity to get hands on with either, all I can do is point at specs and give an opinion.
A big question on some peoples mind is, which camera should I go with if I am moving from a crop sensor (EF-S or DX) body? If you have more than a one full frame lenses from a given brand, stick with that brand, switching is costly and the minor difference between these two cameras aren't enough to justify it. If all you have are EF-S or DX lenses, then that is a different story, or is it? Before answering the question, lets briefly look at the specs of the cameras.
As noted before, the feature set of these two cameras are very close, as will be the price. If you are used to working with one brand, stay with it, otherwise you'll spend time figuring out a new user interface and controls. Seriously, that is my answer to the question of what to do if you are moving from a crop sensor kit. The only reason to switch would be if one brand has a lens you need to have for what you shoot.
"What camera is better though?" some might ask! The D600 has the edge in megapixels, frame rate, viewfinder coverage and the number of card slots. The 6D is lighter in terms of weight, has a slightly higher resolution rear LCD, and a wider native ISO range. The 6D also has a built in GPS and WIFI so you can remotely control the camera from a Android or iOS device.
If I wasn't invested in either system, and looked at specs alone when making a choice, I'd pick the D600. Why? The D600 seems to offer a greater range of features that I would call photography centric. It clearly offers a more flexible auto focus system, a 100% coverage viewfinder and dual card slots. Dual card slots might seem like a minor feature, but having an automatic backup of all images, or having the ability to keep shooting without switching cards on a long shoot can be a big deal. At the end of the day those are the features that matter to me as a photographer, everything else is secondary.