Let's get this straight, I have yet to memorize any specific technicals about my camera (5D mkIII) or any others simply because I don't need to. Now, assuming you know your basic Canon-Nikon history, AF systems is a strong topic in considering either brand. I'm going to avoid that simply because too many people talk about it already. Same goes with ergonomics, its all up to personal preferences, and as such so is color preferences. I have a strong personal connection with the Canon brand, it and Sony having featured prominently in my childhood and are one of two logos that still blaze strong in my memories. And while I have been pampered by some serious glass from Canon (85mm f/1.2L II) that my father lets me borrow from time to time, honestly any glass will work with any brand (brand glass works best with brand bodies, obviously) through conversion kits or whatever you fancy.
A camera is an extension of your eye. It is meant to capture what you see, to preserve what you want to remember, exactly how you want to remember it. Whatever brand you use is what does this the most fluidly. I caught photos on my old EOS 20D just as good as the ones I'm getting from my 5D mkIII, the only reasons I upgraded were focus points, megapixels, and full-frame sensor. It really honestly doesn't matter. Like I said earlier, Canon was a prominent figure in my life growing up, and the fact that I'm using a Canon product to capture my own memories helps tie so strong a connection to my photos and my loyalty to my brand. It's that I feel a continuation of everything, and I'd lose this if I were to shoot with a Nikon. Simply put, take your manual transmission Honda Accord coupe you inherited from your father, keep it in the family for 20 some years, pouring all this money into upgrades and fixtures, then throw it all away for a brand new automatic Subaru. It's still a car, but you lose that connection and familiarity. To this effect, I lose all emotional connection in my photos were I to use a camera I am completely unfamiliar with.
Granted, you could learn to get used to it, but I personally would prefer to be taking pictures in the time spent learning a new system.
I know this was technical like nothing else (total sarcasm), but this was just my two pennies to rub together.