Most pros use either Canon or Nikon. My advice would be to decide right now it's going to be one of those two. Now, which of the two? That's like deciding between Coke and Pepsi. Both will serve you well. Canon users love Canon. Nikon users love Nikon. remember, once you choose, you are pretty much married to that brand as the lenses, flashes and other equipment are not interchangeable. I switched from Canon to Nikon a couple of years ago and it was a very expensive and long ordeal. I am still working towards having the inventory of lenses I had with Canon. But I'm glad I made the switch. I prefer Nikon. The only thing better that I've noticed about Canon is the customer service.
Canon and Nikon are most used for a couple of reasons, one of which I was a little surprised about-freebies.
According to a gentleman with whom I've ridden, as part of Nikon's marketing (and Canon's, although he only works for Nikon), both camera companies have given free DSLR's to newspapers and magazines for their photojournalists to use. Their marketing is first-rate.
I have my (old) Sony A100, which replaced my Minolta 5D, which I'd gotten because I thought I could use the lenses from our old Minolta 35mm cameras. Minolta is no more because of its lack of marketing when they started making DSLRs. Guess they thought their past reputation would carry them, so they didn't follow the lead of the two others.
It is a difficult choice, because there are so many brands to choose from. But, if you want help from fellow photographers, the best club would be between, Canon and Nikon. I have found that you will get the answers you seek from these two photo clubs. I belong to the Canon club of photographers. I like Canon because they are rugged, and will serve you well. The lenses will also take a beating, although I do everything I can to protect my investment. It really comes down too, what do you want to use the camera for? As posted by LouR, the Pros more than likely use these two DSLRs. Look at photos and the ones you really connect with, I would then see what they are using and why. A lot of times you can Blog them and get their opinions. Either way, I find that great photos, are not always taken on expensive cameras. It is the subject and how you introduce it to everyone else. As for my camera, I just purchased a EOS 7D, and am enjoying it to the max. Good Luck! P.S., Remeber have fun and take lots of shots, out of 400, you might get 30-40, or 1, that rocks your boat!