[Nochgo]

If the game is out first, definately watch the anime first. Usually, anime doesn't have time to animate every great things the game has to offer, so if you play the game and then watch the anime, you'd feel disappointed about the anime not being complete or satisfying. Also, if you play the game and then watch the anime, almost everything about the anime will be spoiled to you, lowering the impact anime delivers in crucial scenes, etc. But if you watch the anime first, there will probably stuff in the game that you don't know about, so it would still be a bit fresh. Actually, the opposite can be applied as well though, like anime having filler-like scenes that not in the game.