The MVP2 is a "poor man's ProVari" and that is by no means meant to be a insult. At $40 to $50 they are unbeatable and I think everyone should have one. Even ProVari owners. They are great travelling mods. I use mine because I don't like to take my ProVari's out and about. I also don't like carrying batteries with me.
The ProVari is a nice to have. It's not all that expensive in the big scheme of things, especially considering how much we spent on ciggies. But I only advocate one once you've gotten everything else nailed. Once you get a good topper, good juice, some rebuilding supplies (if you are into it...) and are all set, then buy the ProVari.