I choose voice types based on the personality of a Sim. For manly, outdoorsy guys, I choose the "Warm" voice. For young guys, I choose the "Clear" voice. For really tough, intimidating guys, I choose the third voice. For friendly, young girls, I choose the "Sweet" voice. For middle-aged or funny ladies, I choose "Melodic" and for seductive women, I choose the third voice. This isn't always the case - it depends on the specific Sim and sometimes I'll choose a random one in large households. I like the third voice type for women most and the first vouce type for men the most. I'm not really sure why, though. I like how they sound the most, I guess.