I consider a few different things but it all weighs differently depending on how the run went.

Like if I could feel someone's contribution made the dungeon smoother I'll commend them.

But if it's just a guildheist and things were smooth anyway I'm just gonna vote for the hottest elezen in the group.

Or if someone was just really nice/helpful maybe they'll pull ahead in a raid.

Sometimes I'll toss it to a newbie who asked for an explanation before the fight.

I will vote someone for having a good lore-appropriate character name before I vote someone for simply queuing as tank/heal though.