This can be a heated topic for many photographers, but it is just a choice. For me I chose Nikon because I found my first one within my budget and learned everything I know from toyi with it for weeks.
I upgraded three times from my first Nikon DSLR and now own a main and a secondary camera body.
At this point if I were to switch to Canon I'd have to buy all new gear. I sometimes do envy that eye popping 70-200mm Canon L lens. Its classy, but just a thought.
What do you use or would like to use?