Hi,
Sure. just sharing what i found out. please note, these are just my personal opinions and i'm a beginner of the DSLR world so please do correct me if i'm wrong.
I've Canon cameras for few years from Ixus 50 to Canon G10, and really, i would like to move on to 450D or 50D as most Canon user would prefer because we are so familiar with the menu setting etc.
However, after went into a Nikon's store, i'm successfully convinced by the owner of that shop or perhaps i may just want to try something different. the things that i feel about Canon nowadays, they just want to release their camera around 18 months but they forget about the quality? i was reading the review on dpreview and checking out their reviews. I found that the Canon 50D is basically a 40D but with more pixel and additional HD video, in some certain degree, i think it preforms more worse than 40D. I do not like the fact that the noise on a 50D and its colour particularly on these 2 pictures (warning large file):
Nikon D90
http://a.img-dpreview.com/reviews/NikonD90/Samples/Comparedto/Studio/NikonD90_ISO200_ACR.JPG
Canon 50D
http://a.img-dpreview.com/reviews/CanonEOS50D/Samples/Comparedto/Studio/50D_ISO100_acr2.jpg
If you open both file side by side and at 100%, you will find that the edge of the colour chart from Canon is a bit blurry and the colour is not as shape as the D90.
I also found this problem on my G10 when Canon try to cramp many data onto little sensor, they do make all the data on paper work looks good but they really forget about the quality and colouration from the picture which i think i would concern more nowadays. Although colouration i can actually adjust it on PS applications but why would i spend so much time to adjust every picture?
So with all these minor factors, i decided to use Nikon D90 over Canon 50D. I hope my decision is correct thou.
Lastly, i know a few reefers who use Nikon and take awesome pictures, here is one of them:
http://www.ultimatereef.com/TOTM/2009_june/
Cheers,
Adrian