I have stayed at both properties. The Hilton feels rather tired, it is well located for the town centre but the beach is poor and the ambience is well below that of the Sheraton (busy event aside). Even the Presidential suite at the Hilton would not sway me from the Sheraton. If you must be in town the Sofitel is by far the better option.

You might consider Krabi or further south. This is driveable but it is a longer drive than that to Hua Hin (obviously).

My wife and I love the Sheraton Pattaya (although we hate Pattaya), it is a lovely resort well removed from the zoo downtown, but not too far to get a car to some of the better restaurants etc.