Here's just one example. The specs show that both the D90 and D5000 incorporate a "Silent Wave Lens Motor (SVM)" while the Rebel T1i lacks a "No Ultrasonic motor (USM)". There is just one problem here. NO Canon DSLR has a ultrasonic motor (USM) built into the camera. That's because Canon puts the ultrasonic motor (USM) into the lense.
There is a good side by side comparison of the Nikon D90, the D5000 and the Canon Rebel T1i at:
From the images it looks like the D5000 has more consistent metering, which makes sense based on the 420-pixel versus 35 segment metering system difference. I am surprised to see the Nikon 18-55mm kit lens seems a fair bit better than the Canon equivalent.
The Canon's main strength is related to an advantage for video recording ability if I understand correctly.
With similar prices there are three good choices between these digital SLR cameras and a lot to understand.