Maui can be a lot of fun. It all depends on what the interests are in the group. If it's drinking and snoozing in the sun and the occasional swim I would suggest Maui but it will be more expensive and it's nice to have a car when you are there.
Waikiki is easy to get to from the airport and there are usually more people to gawk at. Prices tend to be lower.
As for my friend:
4 of them are now married
2 of us are in majorly long term relationships
1 is in Iraq
3 are probably unavailabe for consultation due to the fact that their daddy sent them to see their mother in France...punishment or something