Why is that i see more of canon than nikon as of photography?

I was just curious as i get in to night/ club photography. I see more of canons rather than nikon. I have nikon d90 myself, and I was just curious if canon does a better job when it comes to night shot?
Can you guys help me out with the difference in between these two company? How is one better than other?

setting aside from camera, IF nikon d90 is a good to go, which flash / lighting system is good for clubbing shot?

Club photography attracts trendy people. Canon is way better on marketing, having had great success in promoting the rebel as the must-have accesory to the 18-25 year age bracket.

Club photography can be done well with a d90 but also with a 40d as long as you stick a good flash on it (sb-600/430ex at the least) and, preferably, a fast and reasonably wide zoom. Tamron's 17-50 f2.8 is often a first lens for people in this field.

Because Canon spends more on advertising, that's why. They can afford it because they sell the most number of cameras. Their cameras sell because they make sure you know it. You know about it because you see them everywhere. It's full circle any which way you look at it. They are number one in sales no doubt about it but that doesn't mean they're the best.

Difference with Nikon? They do exactly the same thing at maybe a couple of million dollars lower than what Canon spends.

Both Nikon and Canon DSLRs are quite capable in the right hands. The reason you are seeing more Canons is in fact due to the advertising… Of Nikon.

Nikon did a media blitz with Ashton Kutcher touting how great and simple to use Nikon P&S and DSLRs are. The only thing I got out of the commercials is "Hi, I'm Ashton Kutcher… These cameras are so simple, even I can take sensational photos with them" which my brain translated in to "Hi, I'm Ashton Kutcher… If you are as dumb as I'm, buy Nikon and you too can take great photos like me (then after only one week you is are a perfeshunal photeographer and ready to start asking wedding session questions on Y! A)".

Don't get me wrong, Ashton is a funny actor. BUT, I would not buy anything he endorses.

Edit: Without knowing exactly what type of club and what type of situation you are shooting (posed couples/random dance floor/etcetera), it is hard to say. Use some sort of flash diffuser, like a Gary Fong lightspere on a decent TTL flash that is on a off camera bracket and use fast lenses.