red ring on lens is manly
I have to disagree here... the green ring on the lens gives me the "hulk" feel
Joking aside, I think it's a matter of features ur going to find in the camera, and whether ur ready for serious investment in the chosen company's system (unless ur happy with the kit and don't plan to get more lens).
Spec-wise, the D90 is comparable to the XXD level (well, before Canon reset the standards with the 60D).
Therefore, you can expect a decent built quality along that line (The overall opinion on this model is pretty positive, so u won't have to worry too much about it). It also comes with the autofocus motor, which is a big plus nowadays when compared with the D5100-level models. The bad part is that ur stuck with the mid-range specs of 2008.
The T3i/600D is the entry level model for Canon today, so you can pretty much expect entry-level specs of 2011 (which IMHO is a lot more advance than mid-range level of 2008).
Which is better? If you want the built quality, go for the D90. If you want the specs in terms of 2008 vs. 2011, I'd say the T3i/600D will be the better one.
However, if you have a chance, go to the store and play around with both models before u make the decision. I think a lot of it comes down to how the camera feels in your hands.