That's a tough one. It's like asking whether one should buy a PC or a Mac. Canon fanboys will advice Canon and Nikon fanboys will advice Nikon. They are both decent cameras, you may need to go out to the store and choose one based on your gut. Whichever feels like it fits better to you will be the one
I myself have been using Canon for years and having a set of 6 pro lenses, it is a no brainer for me. But that's once again a biased opinion from a hard core Canon user