I've shot Canon for years, and have a modest array of Canon glass, which is motivation not to switch systems. I chose Canon when I moved from MF to AF because, at that time, I felt Canon's L lenses, overall, were superior to what Nikon offered, and Canon's AF technology was notably superior.
But were I starting over today, I'd be very tempted to go Nikon. Although it would take me some adjustment now, I think I prefer the control layout of their bodies to Canon's more button / menu oriented approach, and I think Nikon offers better metering options. (Not necessarily better metering, but more flexibility). In terms of AF, Nikon has at least caught up with Canon, and perhaps bettered them in some respects.
But, as others have said, visit a good camera store and spend some time with bodies from both systems. If you're not familiar with the control structure, let a salesmen walk you through basic operations. See what feels right to you. Either system is capable of producing very high quality photographs; the limiting factor is not likely to be the body. When I first started in photography in the 1970s, a mentor gave me sage advice. He said pick up the camera and play with it. If it feels uncomfortable to you, walk away. It's NOT going to get better.