Matt,
I don't want this to evolve into a discussion of Rustic Canyon, as that we can ALL agree has been done to death, but what I will say is this:
Your criticism of the similarities of the 9th and 10th is irrelevant here - we're talking about single hole merits and my statement was simply that every hole at RC is better than 15 at La Purisima. The 9th and 10th could be carbon copies of one another, but individually, each is still a better hole than 15 at LaP. 9 because of the green and 10 because as Joe pointed out, the new bunkering has made it a much better hole...plus the long narrow green with the shaved faux-green to the left makes it good.
The 15th is a much harder green to hit than 17, but Pete Lavallee is correct that 17 is more difficult to putt with the subtleties and the reverse-canyon tilt in play. 15 to many is the weakest green/link on the course and I'd probably not argue to heavily on that.
On the contrary, I think the par 3 4th is one of the best holes on the course. If you've not played since the HHA was put in on 10, then you've not played since the bunkering and recontouring of the green on 4...the new green is a marvel of design as far as the ground game is concerned and works amazingly well for a running right to left shot to a back left pin. It's no longer just an "upper tier/lower tier" hole, and the bunkering obscures the formerly simple-appearing tee shot. Again, I'd agree with you that in the past the hole was a weak link, but it's been changed for the better, probably to a greater degree than any other hole on the course.
(as an aside, 17 is a great complement to 4, as it rewards the exact opposite shot...often with a similar club)
I'm not saying Rustic Canyon is without fault, but even it's weakest hole (the new 7th, IMO) is still better than 15 at LaP, which I believe to be one of the "worst golf holes on a good course" in So. Cal.