Pat,
In general, almost any bunker and bunker concept should be a bascially equal value in shot making, no? If one hole has a carry bunker, the next a flanking bunker, then a center bunker, followed by perhaps no fw bunkers, then a distance limiting bunker, aren't those all a type of challenge a golfer might have to deal with? Add in the differences of making those flanking/carry/distance limiting ponds or creeks and their bigger penalties, and I think that in general, there should be no two fw with the exact same challenge.
Specifically as to flanking bunkers, I see the need to elongate them down the fw these days (budget permitting) because a flanking bunker at a specific distance challenges so few players. The alternative is to make sure they are placed at slightly different "effective" distances off the tee, since a 266 yd (or whatever) driver hits different distances up hill, downhill, downwind, etc., not to mention they hit it more and less pure with every shot.