I would recommend this be moved to the Hong Kong forum to get better answers. But to answer your question, you've got the Regal Airport Hotel and the Marriott. The Regal Airport Hotel is connected via an indoor bridge while you take a complimentary shuttle bus to the Marriott. The Marriott is obviously the cheapest over the Regal. It sucks that HKG does not have a post security transit hotel similar to Singapore. HKG is known sleeping airport and they should have one.