Ultraman

In what way(s) you think Nikon bodies are better than Canon ones? Or in which particular model(s) you think it is/they are?
There is no absolute "best" one among all brands/models, they just fit different needs and purposes.
From the smaller size to bigger size of the bodies, xTi to 1DSMKII, you still think they can't fit your hand. Then may I ask in what size of your hand is? And which camera body do you think can fit you? Moreover, is the size of the camera body (your most comfortable grip size) your top priority? Then how about the budget, features, quality, choices of accessories.... etc? What is your priority and requirement of choosing a camera?

Ultraman

Yes, camera body is just one of a tools for taking pictures. All the factors such as mega pixel, max shutter speed, highest ISO.... etc features should be considered up to personal needs and preference. And of course, if the hand grip makes you uncomfortable you may not able to hold the camera for a long time and thus it may affect your picture outcome. But I personally won't concern the hand grip much as top priority for choosing my "suitable" camera. Besides the comfort level of the grip, how about weight and size? If you feel the grip is super comfortable but it's 50lbs, what do you think? It should be an overall assessment to fit your shooting needs.
I rarely heard from people to switch brand all because of the comfort level of the camera grip!