Frosslass
Pros-
It has better speed with an extra ghost typing so it has resistances or immunities to some of ice's weaknesses like fighting, & has a HUGE move pool of special attacks like many ghosts
It also has an ability that is perfect for a hail team
Cons-
It also has lower defencive stats (hp/defence/sp. defence) & so it will easily be OHKOed by a fire move
Galie
Pros-
It has a big movepool of strong physical & special moves that compensate for its low stats
It has better defensive stats than its female counter part
Cons-
it just has 80 base stats so it will need choice items or really strong moves to compensate.
It doesn't have the extra ghost typing that can make fighting moves not hurt it.
Over all
I like both but frosslass is the better choice. It has a better speed stat & a better special move pool & is a great spikes supporter with less weaknesses than Galie.