Slag,
In most circumstances where ragged-edged bunkers would look natural, they are also subject to considerable change over time from the wind and from golfer traffic. When we were starting work at Pacific Dunes, Dick Youngscap laughed at remembering how painstakingly Dave Axland and Dan Proctor had been at edging the bunkers at Sand Hills, when they all knew that within a couple of years all the edges would change. He advised us not to waste so much time on the bunkers and just roll with the punches; and yet, the client wants everything to look just so on opening day, and the bunker shapers all take a great deal of pride in their craft, so it's hard to just let the shapes evolve for themselves.
I do believe Merion would be considered differently if Robert Von Hagge or Robert Muir Graves had built their style of bunkers on the site. Indeed, I think at least half of the hullabaloo about the Fazio work at Merion was about taking the plants out of the bunkers and changing the famous white faces ... even though Hugh Wilson may never have seen a broom plant in any of those bunkers. So, in rare circumstances, style wins. It just gets overblown when so many different firms are competing to outdo each other in the same general style.