If you are only getting one I think PS4 would be better for you. For starters you said that's what your friends have, so not only could you play with them you could also borrow their games and stuff.
You also say you like RPGs (such as Xenoblade) and MMOs. I expect the PS4 to get a fair few of those that the Xbox One won't, it already has some MMOs such as FF14 and soon Planetside as well.
Even if it hasn't got the best selection of games yet, give it a year or two and PS4 should easily be the best choice. Greatness awaits...
Bet Shiken that COD would outsell Battlefield in 2018. http://gamrconnect.vgchartz.com/post.php?id=8749702