I have both a V2 and V3. The V3 is way easier to build, the posts are higher. Also the fill port is Philips over flat on the V2. The V2 top is just held by O rings and the V3 is threaded. Forget the metal sleeve on the V3, it's too flimsy.
If you get the V3 don't take the chimney off the cap unless you have some thread lock handy. If you do it may come off instead of the top when unscrewing and you'll end up with a hand full of juice. On both units the air reg ring is a bit loose and you need to fully disassemble to add thread tape to fix if that annoys you like it did me. I really can't tell the width difference on my provari.
Not pushing you any direction. Just the facts Jack.