Some people like water beds. Whatever works for you is okay. If you share your bed, take your partner along for the test. If you order a mattress from one of the 800-number services, make sure you have a comfort guarantee , so that you can return the mattress if you don't like it. A comfort guarantee is a good idea even from a store - though you can never be certain the guarantee will be honored.
Comparison shopping for a mattress is difficult.
But it may not.