It all depends on how many different tones you need. I have both a PODxt and a POD 2.0, and love them both. If you're going to be using it through a guitar amp, I'd go with a POD 2.0 or POD Pro 2.0. If it will mainly be used for recording I'd go with the XT.

There are a lot of threads on this subject, so use the search function and search for POD and PODxt, and you'll find several other posts by myself and many other people on the subject.

As alway's, the best thing to do is... TRY BEFORE YOU BUY!