The Virgin one has a relatively low power CPU (more-or-less equivalent to the original Motorola Droid), has pretty limited internal storage (which means you won't be able to have a lot of apps installed at once*), and has a low-res display. However, the plan is awfully cheap. I personally like Virgin Mobile for calls, but they used to try to screw you on the data. Assuming that the data plan isn't weirdly limited in some way, and as long as you know you're not getting anything near top-of-the-line specs on the phone, I think it sounds like a good deal. I'd actually been considering getting one for the wife (her current phone is a Virgin Mobile dumbphone), but she wouldn't know what to do with it.

* There are ways to get around the limited internal storage, though, where you can kind of automatically install and uninstall apps as you need them, keeping them on the SD card.