Body choices are tough questions. I shoot primarily people in the studio, and secondarily, landscape. I'm a Nikon shooter, particularly now that the D800E and D7100 are out. Does that mean I'm anti-Canon? Nope. I don't like their UI, which is probably the biggest obstacle for me, but if I were to win the lottery, I would have a Canon body so I could mount a couple of the really nice Canon lenses.... my view is that no single lens lineup completely blows away the other and there will always be spots in the line where you might find the grass greener on the other side. Now, if I won the lottery, would I buy the 5D iii? Nope - really the only Canon body I like from an image quality standpoint is the 1DX and I'd skip the rest. At the same time, being really honest, the 5D iii is quite likely one of the best all-around or "pretty good at everything while excellent at nothing" bodies, compared to the D800E which is absolutely world class at studio and landscape photography, and perhaps not quite as suited to event work as the 5D iii would be. So if I were the powerball lottery winner, I might have a 5Diii with that new Canon 24-70 and that Canon 17 TS lens (and probably not much else - I'm really not that blown away by most of the rest of their glass, but those two lenses are fantastic), and a D800E for studio and landscape work. So in some ways, body "roles" have switched lately. The Nikon D700 was a "good at everything but perfect at nothing" body but now the D800E is more of a "perfect for a few things but not quite as good at everything" body. So perhaps this is the difference maker for you.
So ultimately I think you need to figure out what your specific needs are. AT this moment in time, if what I needed FIRST and highest priority was the best current (not future, but right now) AF system in a body that did pretty much a lot of things pretty well, even if it wasn't the absolute best at any one thing, the Canon 5D iii (or better yet, the 1DX) would be the one, if you can deal with their UI (which of course is personal). However, note the emphasis placed on really, truly, honestly needing the very best in current AF system over ALL other aspects. Not "I think I want the best AF", but really truly shooting subjects where it matters. (Not that the Nikons are bad, they are not, but at this time as I write this, I give Canon the AF crown, particularly in the 1DX).
However, now let's talk about backup bodies. I shoot with a D800E with a very small D7100 as a backup. Canon has *nothing* in the AP-C lineup that is close to the D7100 - the D7100 blows away the the 7D (quite honestly with no exaggeration my least favorite current DSLR from any manufacturer). The D7100 is a small viewfinder little DX camera that acts like an FX camera in terms of image quality at lower ISO, which is the first in my experience (and I've shot digital - of various brands, since 2003 and have friends who shoot Canon, Olympus, etc, so I have more-than-just-Nikon experience here). So on the Nikon side, I think the primary body + backup body argument is stronger if you want your backup small and light. And on it goes - you could go back and forth. But if you needed lightning fast, precise, tunable AF, yea, the 1DX is about as good as it gets. But at what point is "good enough, good enough", and that question can be raised about sensor performance as well as AF performance.
Lens wise, since you asked, IMO Canon's best lens might be the 17 T/S. A very specialist lens, but a very fine one. Canon engineers obviously got hacked at Nikon lens designers blowing them away for decades in wide angle lens design and came up with something truly special. The new Canon 24-70 is quite nice, and like all professional 70-200/2.8 lenses, the new Canon there is quite nice. Canon super tele's (the exotic stuff) are also world class too. They have a slightly better 24 TS option too. But the mid line stuff? I'd take Nikons 24/1.4 over the Canon, the Nikon 28/1.8G over any wide Canon makes except the 17, and you'd probably be a buyer of the Sigma 35/1.4 since it's better than either Canon or Nikon, and I definitely prefer the two Nikon 85's, particularly the affordable 85/1.8G, over the Canon counterparts. At 135mm I wouldn't bother with either and go for the expensive but brilliantly excellent Zeiss 135/2 instead, so that's mount agnostic in this discussion.
Ultimately you may need to spend the time and rent each body for a week (certainly at least that long) and see what YOU think. How YOU react and interact to the body and the UI is actually important, as we have to remember the image creation process is important and can often trump the smaller differences in technical image quality. Some people hate Canon UI, some hate Nikon UI. Neither is wrong, it's up to you. But I do think there are sensor advantages to Nikon as well as backup body advantages to Nikon right now, while there are slight AF performance advantages to Canon right now. If your agnostic to the UI, those differences might decide which way to go.
As far as other photographers, I live in a pretty busy southern US market and I travel extensively in the summers. I see a pretty even split between Nikon and Canon, with perhaps a smidge more Canon in the sports market and a bit more Nikon in the landscape market as of late. Most pro's I know don't get into the brand arguments as much as the forum folks do; talk to someone good, they're almost always discussing light, timing, being in the right place, composition, and have the technical side of their craft, for their brand of choice, down so well its second nature, so they don't have to think about it much. They'll switch when something compelling comes out, or often if they get hacked off at the type of pro service they are getting when they need it.
-m