"I realize it's mainly aesthetics, but I have to say that Paul's pics of Portrush are truly magnificent, and I'd argue that those type of sunken bunkers are my favorites in the world."
Mike:
Interesting you say that. They may be my favorites too but only in a playability sense simply because they function so well and are so strategically effective. But aesthetically they look too clean and too perfectly formed to me.
From an aesthetic point of view I think my favorite bunkers are such as surround the front and right of Maidstone's #8 or Friars Head's #10, or along the right of Pac Dunes's #13, or most of Sand Hills since they look like they are just naturally occuring, and primarily because many of them are. 
Tom,
Tough to argue with that. I'm all for the wild and wooly, abrupt and fragment-faced bunkers that you've mentioned, although perhaps I'm seeing a bit too much of that style in recent years.
While they work well on generally sandy, open, wind-blown terrain (as you've seen by the number of natural "blow-outs" occurring en route to Sand Hills, or along the drive to Montauk, for instance), I'm also hoping to see some more variety of bunkering in other settings, instead of the same style copied course to course, even among many of our favorite architects.
The pictures of Portrush Paul provided simply reminded me that there is more than one way to skin a cat, and the elegant simplicity of using little folds and hollows in the terrain to create narrow trench bunkers, or wider, flowing pits that seem to gather balls like catcher's mitts brought to mind how attracted and enthralled I was when I first saw pictures of Muirfield's bunkers as a kid.
Now, there's a open stretch of linksland, (as is Portrush), but would you rather see the bunkers there look like something out of Pine Valley or Maidstone, or as the fairway folding into sand hollows as they are now? It's interesting to think about, and why I'm so eager to see some of Donald Steel's work at Carnegie Abbey.
I guess my overall point is that while we seem to universally love the rugged bunker stylings we see at a Wild Horse or Sand Hlls, or Pac Dune, etc. etc., I'm hoping that they don't become too stereotypical because imaginative variety in our playing fields is ultimately the primary allure of the game for many of us.