I know the D800 has exceptional low ISO DR, but other than that how much better is Nikon for DR than Canon? For most other models, is it really a significant difference in actual usage (in other words, how much difference will it make in print)? And at high ISO, that advantage is lost for Nikon, isn't it? And as for AF, seems with the 5D3 and more recent at least, Canon has become the equal at the very least. I know my 5D3 never misses unless it's user error, and I just got a 6D which in almost no available light it will lock focus perfectly. I don't see any of those being reasons to pick one or the other.
As for the OP, if you are looking to go full frame with Canon, then the original 5D is the absolute bargain camera, it's far superior IQ to any cropped camera (at least up to 1600iso), and you can probably find a good condition one for less than a new 60D, or maybe even a 650D. I'd pair that with the 40mm pancake for the most cost effective, high quality full frame setup to get started with from any camera maker. As you learn to appreciate full frame, you can save your money to upgrade to 6D or 5D3, depending on your need for AF (the 5D3 being better for moving subjects, and the 6D better for low light, stagnant subjects).