Too bad M Alteria doesn't look that great. 130 damage (assuming you use a DCE with a Fairy deck, which is unusual with Aromatisse / Max Potion / Xerneas) is slightly more than Sylveon-EX, buty Syleon-EX doesn't need to mega-evolve and I think heals 50 rather than 30.
Dat Glaceon though... MEGAMAN
Dat Glaceon though... MEGAMAN