We stayed at the Westin Maui as plat and got an upgrade to a Jr. Suite - it was excellent. We visited the Sheraton. I would say that the Westin seems a more impressive property. Yes you can snorkel at black rock, but you can just walk 10 mins for your snorkeling session when you want to do it and still charge the equipment rental to the Westin. I think the beach in front of the Westin was nicer for swimming and the pools are nicer.