Design-wise and stat-wise, I like both pretty well. I've used Leafeon before, and it worked pretty well. But I don't understand their obsession with making them impossible to use in-game (without trading) by waiting so late to evolve.
DP didn't include Eevee, so you couldn't get them until after the Elite Four. Platinum gives you early access to Leafeon, but you're stuck with an unevolved Eevee until just before the seventh gym if you want Glaceon. HGSS not only doesn't include them in the Johto Pokedex, but you also can't have them after the Elite Four, because there's no areas to evolve them anyway.
BW, like DP, doesn't have Eevee, so you can't use them until after the Elite Four. BW2 includes Eevee, but both evolution locations are only accessible after the Elite Four.
XY gives you access to Glaceon near the seventh gym, and to Leafeon near the eighth gym. ORAS gives you immediate access to all Eeveelutions as soon as you can get Eevee, but that's not until right after the legendary Pokemon crisis, right before the eighth gym.
This is just ridiculous. It'd be one thing if the other Eeveelutions were treated like this, but they're not; every other Eeveelution can be evolved essentially immediately in every game they're in.