The D600 looks nice. What I like most about it are the small size, faster frame rate, and that they stuck with a 100% viewfinder. Small size is a big plus for back up bodies, and for most people upgrading from crop. Plus, it's still weather sealed. High ISO looks good, about the same as D800 honestly. We don't know yet if it's the sony sensor, but the look of the chip itself does look like Sony Exmor.
Too bad it doesn't have a movable screen.
The Canon 6d (if that is the name of it) could be great. We don't have enough info yet. The 11 point AF might be good. The rumor specs don't say if the other 10 points are cross, just that the center is 2.8 cross. We also don't know about the sensor, yet. A new 20mp sensor could be great, if it has a new high dynamic range design. If it doesn't, it's a fail imho. Also, I'm a huge flip screen proponent, so if it has one, that's a plus. If it has a higher dynamic range sensor, 11 cross points, and a movable screen, and comes under 2k, that's a win in my book. If it has the same tired dynamic range, only the center cross, and no movable screen--yuck.