My view - stand on soapbox - all these treatments are very good paint treatment/polishes, BUT they are not worth the cost the dealers charge always around £300.
Supagard & Diamondbrite are similar, what makes them good is that they are easy to apply and easy to finish, they would have to be otherwise dealers wouldn't be using them regularly. For initial cleans they do make a difference, however I'm with John over the long term benefits.
Mike