>How much would I be missing if I go for the English translation?
Dunno, but they can't have done such a terrible job that u miss out on the story. There was an earlier MTL translation of the game and they probably wanted it to have a more "proper" translation in the first place.
It's more likely that a perfect translation won't give the same general feeling u'd have otherwise while reading. It should probably be better than reading MTL'd text and that's it.
Unless you intend eventually lerning nippongo, I say go for it ヽ(´ー｀)ノ