I've owned both (still own the Tonelab), and found the Tonelab to be much more faithful to the way the real amps that it emulates would sound. BUT, this is not what most people are looking for when they get a processor.
People seem to buy the POD to get the "radio-ready" sound, compression, FX, whatever, and that's generally what it gives. I've talked to many people who think that the POD is best, and if you want something that's easy to use, and gives you a "predictable" sound, go for it. When I owned it, I didn't go too deep into editing, since I wasn't entirely happy with it's sound to begin with.
The Tonelab, on the other hand, has really blown my mind with the way it sounds. Instead of the Hit Single sound, you are given a nice selection of amp models that sound like the amps after they've been miced up, but before any post processing. I like this better, because even though my gear isn't top of the line, this feature, or whatever you'd call it, makes it feel like I'm working with a real amp, so I can use much of the knowledge I gained from working with real amps, which in turn gives me a much better sound in the en d than the PODxt.
And before I ramble on forever, Snapper, Guitar Rig does come with a USB footpedal (and honestly, I think it does sound better than both the POD and Tonelab, but can be a pain due to CPU usage)