xl2 is a standard def camera. The XLH1 is the High Def offering in that line. Both are good cameras, the Canon will look more like a big professional camera on set. This is a consideration with pros and cons. The pros are that you will be taken more seriously by people on set (if you haven't worked with them before) and by passersby. This is also the con, It's harder to shoot guerrilla style if you have a big piece of hardware like the XL series of camera.
The HVX with P2 cards also means you have to have a workflow that will support the P2 cards, so You'll need to add extra days into your rental to use the camera as a deck, whereas with both cameras, if you record to tape, you'll be able to use any HDV camera to import the footage. The drawback is that there's heavier compression on HDV to tape than HD to P2, thereby slightly lower quality... this really only matters if you're projecting it on a large screen, transferring to film or doing lots of heavy post/fx work to the footage.
