Need help choosing pokemon

[Demonion]

Oke i currently have heracross - slowbro - zangoose - umbreon - weezing - porygon2

But i need help with (maybe) replacements for slowbro:

Slowbro@Leftovers
Modest
EVs: 200 HP, 200 Sp.Def, 72 Sp.Atk, 38 Def
(Own Tempo)
~ Calm Mind
~ Surf
~ Psychic
~ Rest

OR

Starmie@Leftovers
Modest
EVs: 252 Sp.Atk, 252 Spd, 6 HP
(Natural Cure)
~ Surf
~ Psychic
~ Cosmic Power
~ Recover/Rest

Plz suggest what could i use better? I know most put thunderbolt on starmie but i already have porygon2, but if i should put it on starmie anyways tell me :)

 

[Frostweaver]

I choose Slowbro...

a) it's a UU so it's not hideous like Starmie
b) a lot better tanking ability compare to Starmie, even if Starmie got recover and Slowbro doesn't...

Starmie just cannot tank and sweep at the same time, but Slowbro can do that. Plus, this team needs a special sponge anyway so Slowbro will fit nicely.

 

[Kairi]

Slowbro is OU I believe. @_@; It's a great psychical sponge for the likes of Aerodactyl and Ttar, plus Calm Mind.
Starmie can't do the Cosmic Power thing—too low of HP and quite a few weaknesses. You could give it Rapid Spin—threatens Skarm and Gengar(which is used to stop RS)

 

[Frostweaver]

At least according to SF list it isn't =p

Plus I see more Starmie than Slowbro...

If Starmie is going to cosmic power, it has to drop all speed and offensive power to give 252 hp and the rest in defense, or else it's pretty useless for tanking purposes.