I spent a long time looking at both, I had people tell me the pro's and con's of both, in the end it came down to which felt more natural and comfortable, and which had menu's that were quicker to go through and easier to use. I love how the nikon sits, and how i can change all my settings with one hand while still ready to shot, (massive fan of the thumb+index wheels), the nikon's a bit bigger and feels nicer to hold too. the menus are easier to flow through aswell, plus i can create my own menu's and assign buttons if/when i need to. that's pretty much how i came to my decission.
Oh... and i have a lot of nikon glass at work i can borrow from time to time. which is handy