You know they have these wonderful things called ear plugs?As a courtesy, stay away from the ported clays guns, your friends will appreciate their hearing in 5 years-
I too think it's a waste of money. None of my guns are ported. However, I've never noticed that it makes shotguns obnoxiously loud (definitely louder though).
Go handle as many shotguns as you possibly can. Get someone with experience to come with you, so (s)he can ensure you pick the gun that fits you best. Remember: fit is everything!
That's the only advice I can give.
I too think it's a waste of money. None of my guns are ported. However, I've never noticed that it makes shotguns obnoxiously loud (definitely louder though).