Power up ?

For attacking 2 and 3. For defending 1 and 5.

For me only the 1. Snorlax is good enough to spend dust and candies, -IMO.

Definitely 1. Good attacker and defender. That body slam is the destroyer of worlds

1 > 4 > 2 > 5 > 3 in that order. But the only one I would really power up is number 1. You could make a case for number 4, it depends on your other grass type attackers.

power up nothing, wasted stardust

1. His IVs are a tiny bit low. However he'll still make a beastly defender. As long as you don't have a bunch of other defensive Snorlaxes I would power him up.
2. Did you miss an x? If he's 215ish cp then I would say he's going to eat far too many candies to be worth it. If you did miss an x I would say he's probably powerful enough as he is to decimate anything, so he doesn't need powered up, though you could and not feel bad about it.
3. I hate mismatched movesets on attackers. I would not power him up.
4. This guy is pretty serviceable as a Vaporeon counter as he is. If you don't have any other good prospects for countering Vaporeon you might want to power him up.
5. Ehhh... Good IVs, best defensive moveset... but Venusaur isn't a brilliant defender. If you are really hurting for defenders, you could. I wouldn't power him up though.

tl;dr: 1 > 4 > 2 > 3 > 5

Def not 2,3,4. Wasted stardust.
5 is best possible plant defender except exeggutor. If you want to be optimal, don't power up any plant Pokemon except exeggutor. Otherwise, If you are happy with 87IV power it up to max. I would personnaly do it.
1 is very strong. Best defensive moveset. IV a bit low though. I would wait until having 250k dust and 150 snorlax candies. If no better IV snorlax then, I would power it up to max