Darn! Just when I was on Step 10 of 12 on this subject and progressing soooo well!
Thanks, Tom. 
In truth, you ask a fair and balanced question and let me try to address it in a couple of different ways.
I believe that bunkers should serve 3 purposes.
1) As a visually psychological hazard
2) As a real hazard in terms of playability, as you suggest
3) As a visually pleasing art form in natural harmony and cohesion with its surrounds.
Let's use your example and examine each area. Visually, a hazard should draw the eye and let the player know in somewhat uncertain terms that this is something to avoid. This can be achieved through the obvious (depth, steep walls, gnarly internals and surrounds), or it may be more subtle like the shallower bunker that might not look so fearsome but leaves an awkward recovery because of the angle of the next shot, or the green running away, for instance.
Still and all, unless a bunker gets into the head of a player, it misses the opportunity to function in a way that consciously affects play.
I believe the newer style, rounded, more manicured, more consistent bunkers (at any course) lose some of the psychological impact because the player is almost always assured of a clean, flat lie. Better players, in particular, are not as easily intimidated by bunkers either, even deeper ones, due to these factors.
In most newer-style bunkers, they are no longer hazards. They are simply another well-prepared, maintainted "playing surface", largely separate but equal. They just require a different type of "shot" from the better golfer, and thus lose much of their psychological impact.
On the other hand, let's take the inconsistent, wild bunkering of Pine Valley (which the old bunkers at Merion shared similarities with). Because the golfer can never be sure what type of lie, stance, or other impediments might come into play if one goes there, they still serve the mental purpose.
It's the inconsistency and unpredictability that made them hazards in the first place. With that element removed, the excitement is largely gone.
From the perspective of playability, certainly deeper bunkers can play more difficult, particularly the fairway bunkers. Still, I prefer to see fairway bunker where the player is tempted to try to still reach the green oftimes, with a razor-thin margin for error. It's that type of decision making that fairway bunkers function best as. If the only option is to blast out to the fairway, that's certainly one function of bunkers, but a limited one in many respects.
I'd also state that deeper bunkers at greenside generally don't have the same penalizing effect on the better player, particulary in these days of 60 and 64 degree lob wedges. Give a good player a clean, firm lie, and you'll generally get the consistent, expected, good result.
Finally, just as a totally subjective exercise, it's been a real thrill in recent weeks to see just some fabulous, rough-hewn, gnarly bunkering at places like Gil Hanse's Inniscrone & Applebrook (w/kudos to Rodney & Bill K.), Ed Carman's Running Deer, and Archie Struthers Twisted Dune.
Besides being psychologically and visually striking, as well as ruggedly natural and in harmony with their surroundings, they also seem to offer the type of inconsistency and certain uncertainty that make them play as hazards for all levels of golfers.