I would offer additional refinement.

A pretentious person is a person who thinks they're "better" than others (whatever that means) for irrelevant reasons, like their taste.

A poser is a person who in addition doesn't have the good tastes to be better than others, and so he fakes their tastes. He's putting in effort in order to attain pretentiousness.

I would define hipster as synonym of poser. It's worse than pretentious.