Which Eeveelutions are worth maxing out?
Eevees are very common here, it's not very difficult to find one with 800+ CP.
So, which of these are worth maxing out, assuming all are level 30?
1: Vaporeon WG/HP
2: Vaporeon WG/AT
3: Flareon FS/OH
4: Flareon FS/FT
5: Jolteon TS/TB
6: Jolteon TS/DC
7: Espeon C/FS
8: Espeon ZH/FS
For me, I will max out 1 each of all of them except TS/DC Jolteon, and keep the rest at 30.
Answers
If you prefer dodging in most battles:
Vaporeon with WG/AT
Flareon with FS/FT
Espeon with ZH/FS
If you prefer spamming attacks:
Exactly the opposite of the above movesets.
Jolteon, you can power up either of them. Discharge is less risky, but Thunderbolt gives more DPS and is not as risky as Thunder. Both are useful in raids.
If by maxing out you mean taking them to lv 39, I'd say none.
We are severely hamstrung by stardust right now, and getting the marginal cp gain is no longer an issue in the new gym system, so nothing is worth the astronomical price of powering up to lv 39.
Even if you are swimming in stardust right now, sooner or later you will run into a shortage, unless you plan to power up only these Eevelutions and not a well-rounded army, which I doubt is the case.
If you have sufficient stardust as well as sufficient candy, I would recommend maxing out the following:
1: Vaporeon WG/HP
3: Flareon FS/OH
5: Jolteon TS/TB
7: Espeon C/FS
But you need to be careful with the rarity of stardust and should choose which of the above based on your local biome.
Personally, I am in a water biome and keep maxed out versions of 2 x Vaporeon, 2 x Jolteon, 1 x Flareon, 1 x Espeon and I am considering what to do with Umbreon.
