I have pokemon Y. It's a fun game. Here's some version exclusive just in case:
Pokemons in X Only: Staryu/Starmie Pinsir Houndour/Houndoom Poochyena/Mightyena Aron/Lairon/Aggron Lileep/Cradily Anorith/Armaldo Sawk Swirlix/Slurpuff Clauncer/Clawitzer Xerneas
Pokemons in Y Only: Shellder/Cloyster Omanyte/Omastar Kabuto/Kabutops Heracross Larvitar/Pupitar/Tyranitar Electrike/Manectric Purrloin/Liepard Throh Spritzee/Aromatisse Skrelp/Dragalge Yveltal
Mega evolution is X Only: Charizardite X Tyranitarite Manectite Pinsirite Mewtwonite X
Megas evolution in Y only: Charizardite Y Agronite Houndoomnite Heracronite Mewtwonite Y
I'm not 100% sure on the exclusive mega evolution, so i may be wrong. I would recommend checking out the exclusive pokemons and choosing which one is your favorite
Get both! My brother has X and I have Y. I think Y is fun. I would personally keep Y. Now, if bạn wanted to battle someone with a Xerneas and bạn have a Yveltal, bạn would lose HORRIBLY. I like Pokemon Y but Pokemon X is also a great game.