Water Gun is Vaporeon's only primary move so all your Vaporeon's should have that. Assuming that you meant Hydro Pump instead, the answer depends on several factors. What is your trainer level? Aqua Tail is not much worse than Hydro Pump to begin with and Aqua Tail has smaller dodge window making it stronger in some cases. Despite Hydro Pump dealing a bit more DPS, I've seen some people prefer Aqua Tail anyway. My best answer is to get 2 Vaporeons with different moves. It is also possible that further changes are made to moves so I wouldn't recommend powering up both of them if they have the same moveset.
Vaporeon
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)
By now I evolved four Eevees into Vaporeon, two of them with IV 100. But non of them ended up with water gun. The two Vaps with IV100 have Aqua Tail. Should I stick to one of them and level up or is it not worth it?
Try again? (and again...)