Oh, I'll have to disagree strongly with that prick...no wait!
I appreciate the discussion, and threw it out hoping for such. It is a worthy topic, but it will still be hard to quantify.
I was really focused more on just how different design styles really are.
For a moment, let's keep it to the golden age so as not to make anything too personal. In short as they designed, the practical constraints of golf development in that era forced them into many of the similar patterns.
For example, some say Ross liked clubhouses in corners. I say he was forced to place them there often (as were others) because that was the shortest utility run. As an example, Northwoods in Duluth is north of town and is it any wonder the clubhouse sits on the southernmost parcel of land where the utilities probably were already existing?
As I have said before, when I look at the GA books by Ross, Tillie, Thomas and Mack, I see sketches that look amazingly similar. I don't know who led and who followed, but the theory of strategy and play seemed similar in major elements - notably the zig zag fw, the angled carry bunkers off the tee and the frontal openings.
That said, you can sure see differences in a Ross to MacKenzie to Thomas course from the bunker look alone. Tillie is hard to categorize. Ross was conservative while the others had more flair with their bunkers, making overall, their courses better to my eye. So, the courses are similar, and yet I have my favorites.
But as stated, even their bunkers had more in common than they had differences. All had about the same amount of bunkers on most courses, the same scale, similar theroetical placement, depth, edge treatment, sand color, etc. For those who like CC bunkers, all of the above is true, generally, and the big difference that attracts your eye is the "chunk" edges, which are (or at least were) to them.
Taken in context of ALL the design decisions that were made about the bunkers on all courses, or even by measuring the square footage of chunk edge as a portion of the total, I think that that is not much a piece of the pie, design wise.
But if bunkers are 10% of design, and edging is 10% of bunker design, the design difference is 1%. If you like that bunker style, or if that was your biggest criteria in determining whether YOU like a design, you might very well overinflate the actual design style differences between CC and PDG if they designed side by side courses.
And, of course, you wouldn't be wrong! And, its not impossible to see that the whole can equal far more than the sum. Lastly, such a numerical evaluation system falters when going on gut feel about what you like.
Don mentioned that PDG designed what seems to be their standard development course on an ocean front site down in Port Aransas ( I assume this is the one. BTW, years ago, when there was a different developer, I had that job, so I am familiar with site) If PDG did infact ignore the natural setting there might be more than 10% design differences! However, knowing the site sat so low to sea level, I can attest that merely laying the golf holes on the existing ground wouldn't have worked, and extensive grading was necessary.
So whoever got the job would have done some grading, perhaps a different routing, etc, although even there I presume they would have found some of the same holes.
Any evaluation presumes that the gca's interviewed would all come up with decent routings. Comparing what might have been to what became, is pretty difficult. But given that most gca's would come up with par 70-72 and at least 7000 yards from the back tee, I propose that the routings could be deemed within 10% of each other. If routing is 25% of the design components (if done badly, it could be more) and you preferred one routing to another that was 10% difference, there is a 2.5% difference.
The differences just aren't as much as we all presume, based on some pet features we like. Even a Doak green at 4% isn't that much different than a Brauer green.
Tom Doak if a fine gca, and if a Tom Doak course is 10% better than other signature gca's on average, it is a huge design advantage, even if its a single digit number of %. Fazio courses, for their style and market are 10% better than others, BTW - he rarely misses on details. I actually think the top 10 guys have less actual design differences than the next 10 - 20 - and some of those are created with the extra budgets they get - but that marketing by any hot gca convinces many that the differences are much greater.
Again, the topic is too theoretical to spend much time in more detail, but it support Mike Y's contention that Greg Norman or any of the others is hired more for the name than the design quality or even style, since so few even know what they like, or whats "good." In fact, they probably hire Doak, Fazio, or even Weiskoph as much because they are "currently trendy" than for any other reasaon. But, that's just a guess and I realize it does seem a bit cynical on my part.