When I started off, I had a choice between the two biggest -- Canon and Nikon. And I sort of went for Canon. It was nothing more than just a choice; it was at that time a non-educated choice. So Canon was the choice for me and because I have invested so much into lenses and paraphernalia, I don't change gear much. So in other words, the lenses that I bought seven, eight, nine years ago, I still have. I only add to them. What changes really is the camera only because they come out with better models every year. As for other gear -- I do audio recordings -- I look for what is recommended on the web.
On a typical trip, I carry a Canon 5D Mark II, a Canon 1D Mark II, a 70-200mm f/2.8, a 24mm f/1.4, a 28-70mm f/2.8 and a 17-40mm f/4.0. For audio, I use a Marantz PMD620.