Tom --
Oh gosh; an unfair thread opening question. But, since you asked . . .
In the very early 70s i was a part-time PJ in college, and stringer for local papers, etc. i shot mostly Nikon Fs owned by others. Clunky, heavy, but always worked; stone-cold reliable actually. At the time i always suspected that the Canon FDs were better (particularly their lenses) and good-golly-miss-molly were the OMs sexy; almost like a Leica. Pity that the shutter dial was around the lens collar (which, after some years of shooting, i couldn't abide).
I graduated and didn't pick up a camera for almost five years. When i wanted one I boiled it down to an OM, Pentax MX, or the then-new "smallish" Nikon FM. i, correctly i think, chose the FM due to lens flexibility and long-term durability. This would be about 1980.
I am sure that my art would look the same with Canon. But Nikon has generally delivered over the decades for me, while being, ahem, a somewhat clueless a company as they are. To this day i marvel at the shadow detail in the Raw files, ergonomics, durability of the gear, and -- a small-ish thing i guess -- the CLS system. When i absolutely must get the image, i reach for the d600.
But if ah gotta carry it all day it is my m4/3 kit; which is another topic.
My biggest knock at Nikon is that i still wish that we had the Canon lens options. I care more about lenses than bodies and would gladly trade the Nikon lens portfolio for Canon's.
-- gary ray
Semi-professional in early 1970s; just a putzer since then. interests: historical sites, virginia, motorcycle racing. A nikon user more by habit than choice; still, nikon seems to work well for me.