After reading a mind-boggling number of MVP fanboy posts, I'm thinking I'll have to try one out. But I can't comment on them from personal experience.
I scored a couple Vamos from slowtech for $50 each with Nitecore I2's and Sony 10 amp batteries for the wife and I - love 'em, and can't beat the price with a stick. I also wanted to dive into mechs at the same time as APVs when upgrading from Ego twists, so the battery charger and included external batteries were a plus for me (supplemented with Sony VTC5s from MBV at $20/pair).
The 5 click on/off function is a little sensitive on my Vamo, the buttons are a bit loose, and I've had to use a paper clip to pull up the positive pin a couple times in the month I've been using it, but I couldn't be happier for the price I paid. No major spills, but I do use it on the job site and it's survived a few knocks and bangs.
I also picked up a 510-USB connector for the Vamo, so in a pinch I could kill my vape to power my phone if it ever comes to that...but I'd be hard pressed to figure out which one I'd rather have in an emergency situation.
tl;dr: I don't think you can go wrong with a Vamo, but the MVP pushers make some compelling arguments. If you have no interest in sharing batteries with mechs and box mod v. tube mod aesthetics makes no difference, methinks MVP might be the way to go, even though I've never tried one.