I don't think saying one is "better" or one is good or bad is necessarily appropriate; they're different. There's things I like about XT, but hate about v2 and vice versa.
I'll probably sound like I've been smoking crack here, but bare with me...
To me the Pod 2 sounds as a more "already recorded" tone if you will, where as the XT is a brighter, livelier sound. Some sounds are better on one, some are better on the other. At it's worse, the Pod 2 can sound slightly wooly and dull, the XT can sometimes sound a bit harsh and digital for me anyway.
The big plus for the XT over the v2 is it's way more responsive to play. v2 sometimes just feels like you're not playing on a real amp....it's weird to describe.
Hope this helps.