Its personal preference and loyalty to be honest. I’m a Nikon guy because my Uncle (professional photographer for 30+ years) and my father (Professional photographer for about ~20 years) both used and loved Nikons. Granted this was in the day of 35mm film, but because of that I have remained true to Nikons and especially after having used my Uncles D700? (Not sure what it is, not a 7000… but it has a 7 in it IIRC)
I have used both Nikons and Cannons , and its more about feel and user interface and features.
Either camera in the same class with a professional photographer will for the most part perform the same, some things and setting and conditions may differ for each camera but it all seems pretty standard these days.
Matt, get a cannon IIRC the price for a cannon that also takes good video is considerably less then a Nikon… To lazy to look right now, but last I looked pretty sure you couldent find a Nikon that takes HD video for less then ~1100
I’ve never used a “cannon” (well, maybe a potato cannon) but I have used a Canon. I have nothing bad to say about them at all, I even have an ancient miniDV cam thats a Canon and it always worked great. I have little to no experience with SLR cameras so I’ll remain mute on the subject otherwise. KTHX.