Check the Hilton Sorrento thread to get an idea on lounge and Diamond treatment. They got lots of cruise guests during the season (May - Sep or so). Most reports will be from last year or so, but it is nothing out of the ordinary lounge offering and F&B wise from what I recall reading. That and the frisky pricing at the Hilton made me decide for SLH (Angiolieri though versus Cocumella).

For similar pricing, I'd pick the Hilton last, but we like smaller, more intimate places / properties so one of the SLH ones suited us just fine.