Was at the Hyatt last week and went by the MArriott--
The Hyatt is a much nicer hotel--the MArriott is definately showing its age and looks a little too touristy for me. The Hyatt upgraded me to a ocean-view suite (Diamond status) and the regency club was nice (overrun with kids though)
The two hotels are about 1/4 mile apart, but not really walk-able at night b/c the path between the back of the two doesn't connect unless you want to walk on the beach