Oh, man, so many ways to take this somewhere, ....
We expect that after Gen4, male Kirlia will evolve into Gallade, a fairy/fighting pokemon, while female Kirlia will continue to evolve into Gardevoir.
My take is that Gardevoir is more powerful, the Fairy/Psychic typing is very strong, and Gardevoir is probably the only high CP user of Dazzling Gleam with STAB (same attack type bonus). Weaknesses to Bug, Ghost, Poison and Steel aren't that bad, Dark makes her somewhat vulnerable (and Ghost to SB Mewtwo).
Gallade could be really good if they give him a strong moveset, like Counter/Dynamic Punch, but an inferior moveset could mean he's less useful than Hariyama. Hard to say right now.