...german obstacles were more visible and could be destroyed/avoided

...but mainly, the low tide rose fast, and allowed for the ships to deploy troops, and get out of there quickly.

The massive disadvantage was they then had incredible distances of beach to traverse. Germans had clear, unobstructed fields of fire, plunging downward on the landing craft....

A few years ago I took a group of BYU Army ROTC cadets to Normandy. We went to Omaha beach at low tide. For effect, I had them sprint from the water's edge, to the embankment. They were well rested, dressed in casual comfortable clothing. These were fit young people. At dead sprint it took them over 65 seconds to SPRINT the long, flat open beach. Afterwards the reality hit us all. Quite a powerful moment to realize the audaciousness task each of the early troops confronted. Impossible really.