Canon Digital Rebel XSi and Canon Digital Rebel XS comparison?

Is there really much of a difference? Which one is better? What Nikon model would either of these be the most similar to?

I own a Rebel XS and it's an excellent camera. About the only real difference is the mp count.
But don't get caught up in what we call the mega pixel myth - that is, more is better because it's not necessarily true.

I've had my XS for well over a year with excellent results like this.