If someone makes me laugh, they'll get it. Most of the time I'm so nervous about going into a dungeon that I really appreciate someone who is lighthearted. Outside of that, I will normally pick based on how well someone did their job especially if they're new. If everyone was around the same quality, I'll choose to give it to another Roe or an Elezen if there is one of either because they're pretty scarce on my server.