Froslass
HP 70 250 - 344
ATTACK 80 148 - 284
DEFENSE 70 130 - 262
SP. ATK 80 148 - 284
SP. DEF 70 130 - 262
SPEED 110 202 - 350
TOTAL 480
Abilities : Snow Cloak Cursed Body (DW)
Glalie
HP 80 270 - 364
ATTACK 80 148 - 284
DEFENSE 80 148 - 284
SP. ATK 80 148 - 284
SP. DEF 80 148 - 284
SPEED 80 148 - 284
TOTAL 480
Abilities: Ice Body Inner Focus Moody (DW)
Well if you want a looking at Glalies total stats they are exactly the same as Froslass's stats but Froslass is far more dominant in speed giving it and edge over Glalie. Also if Froslass has Snow Cloak then it has a high Evasiveness which is useful when you are attacking but then isn't it useful for everything? (Rhetorical question) This would have to be in Ubers though. For OU you are left with Cursed Body which is useful if you give Froslass a Focus Sash then hopefuly if the opponent uses a move that is super efective then it will get Disabled.
I would choose Froslass
Ofcourse it is up to you though.
Hope this helps