First is the quality. The translation of a game is a creative process, and you can't do it if you don't like the game. We had a case where a translator messed up badly in every way, from deadlines to quality, even though we were very happy with his work on another project. We asked him directly what the problem was, and it turned out that he didn't like the most recent game, but played the previous game frequently with his wife, and even organized mini-competitions. That was when we understood that it's very important to take the translator's tastes into account, as it has a significant effect on the quality of their work.