Even if you rebuild the heads for the Protank, it's astounding how one is amazing and the next, seemingly identical, is just plain bad.
I agree with this 100%. I rebuild the heads on both my protanks and vivi's With the Vivi's I can get constistant good flavor. Not so much with the protank. My ADV are 100% VG and I just can't get the flavor from a protank. The vivi's actually work really well in this regard.
I want the protank to work. I love it's design and the way it looks(especially the PT2), but I just can't get consistant performance out of them. I really like that you can change the heads out without emptying a tank. My juice gunks up the coils with a quickness and it's nice to be able to just swap them out. I can do it on the vivi nova's but it's way messier.
That said, I don't want to sacrifice flavor for convenience, so for me the Vivi wins. It's my go-to tank (until my IGO-L gets here anyways). In another 6 months there will be something new that will outperform both. I actually see myself gravitating to the genisis style(but that's getting way off topic)