Iv vaporeon

Aqua Tail is fine in my opinion. I get that WP is the "best" defensive move but everyone that fights Vaporeon either knows how to dodge it all, or uses a grass type and doesn't even bother to dodge anything. In either case Water Pulse really doesn't do anything more than Aqua tail.

20% IV will make about 80-100CP difference at max level.

It's a tough one, but I'd probably go with Water Pulse. What are their CP's? Does one of them require a lot more powering up than the other one?

Either will do just fine on defense. Knowing nothing else, I would probably recommend whichever one currently has the higher CP.

Two other thoughts: 1. If you level the aqua tail one, you'll be able to use it for either attack or defense. 2. As TTT said above, if you're looking to level a Vaporeon all the way to lvl 30+, the higher IV one will end up getting placed a little bit higher in gyms, so it will be marginally more secure.

Both are good with high CP, but the AquaTail one is better. Event if water pulse is better for defense the IV difference will give you the upperhand.

For defence Water pulse is better, but Aqua Tail isn't bad, and is my favourite attacking move for Vapes.

I'd invest candies in whichever has the higher CP if there's a difference.