Well, let's compare them.
HP 68 HP 68
Attack 65 Attack 125
Defense 65 Defense 65
Special Attack 125 Special Attack 65
Special Defense 115 Special Defense 115
Speed 80 Speed 80
Gallade has a great Attack stat and can get a boost from Swords Dance. It also has a wider movepool than Gardevoir due to it being a Fighting-type as well as a Psychic-type.
I've got nothing to say about Gardevoir. It has a very good Special Attack stat and can get a boost from Charge Beam.
This is what I think:
Gardevoir<Gallade simply because of its wider movepool and it being a Fighting-type.
But if you like special attackers, go with Gardevoir.