We've found it better to stay at BanPhe and take the ferry over to Samet for a day on the beach and leave again on the 5pm ferry, primarily because the accommodation on Samet is so expensive. At BanPhe an AC chalet in a garden resort costs us 500-600Bt, on Samet you get a dog kennel for that. Also at BanPhe we have more choices of restaurants/shopping at lower prices.
The nearest real paradise to BKK that I've found is Sunset Village Resort, between Jomtien & Sattahip. It's expensive (4000-5000Bt a night) but really fits the bill on being a paradise, they've even brought in white sand to tart up the beach. If you Google Sunset Village Resort you can check it out. It's hard to find so you'll need to organize pickup.