Nikon d90 with 50mm 1.8f or canon rebel xs 50mm 1.4f?

I want a really nice camera that takes really good quality in-the-moment pictures. Which one is better?

The nikon d90 is better. Look at the specs comparison if you don't believe me -
http://snapsort.com/...-Nikon_D90

People like to quote lab results and that's fine but it's not really what counts. What counts is the result you see with your own eyes.

For me I'm a Canon guy because I like their gear and the quality of it.

So why the particular question about the different lenses? Are you buying the camera used?
Canon also has an f/1.8, I own and especially considering the price it's an excellent lens.

I only recommend what I own and therefore know.

The Canon XS the lowest grade possible low-end DSLR (about equal to a Nikon J1 in image quality). The D90 is a far better camera.

Pick them up and find out. Only an idiot would close his mind to Pentax or Sony at this stage anyway.

Between these two older models, the Nikon d90 every time. The Nikon is a mid range dSLR. The XS is a cheap entry level model. The D90 was the first dSLR to shoot video. So it's not the best, but it works. The XS has no video. The image sensor in the D90 is a superior Sony image sensor.