Quick question for any experts here. I am looking for a 'midrange' DSLR--basically either the Canon Xsi or the Nikon D90. I know the D90 is almost twice as much as the Xsi...but my question is more general. Can someone tell me what the 'big picture' differences are between Canon and Nikon camera systems--not necessarily between the 2 specific models mentioned above. Rather, once you select a brand, I am assuming that I am basically stuck with that brand. What I am mostly interested in doing is taking a lot night outdoor pictures (skylines). I know that Nikons have higher ISO ratings, but does this REALLY make a big diference. I also know that the Canon EF-S lenses are not compatible with standard Canon cameras--not really a big issue for me. But what I want to know is if you give up on certain things if you go down the Canon road vs. the Nikon road? Any things that are 'special' about each brand--in general? Thanks, BJ Wanna kill these ads? We can help!