David -
When and Where are you playing - These courses, though all north of LA, are not exactly neighbors
I've not played Sandpiper
Between Rustic, LaPurisima, and Hunter Ranch, I'd probably rank them:
Rustic Canyon
La Purisima
Hunter Ranch
And that's no knock against Hunter Ranch...I have a tough time choosing between the two courses. If I could pair the front nines at Hunter and LaP together, I think you'd have a great course...the problem with Hunter is that the back nine tries too hard to be gimmicky (ponds, horseshoe par 5s, etc)
The problem with LaP is that the tee shots on the back nine get really strange - 10 has a weird cross-hazard, I think it's 12 and 13 which together make up a duo of really bad tee shots, the latter of which takes driver (and possibly 3 wood) out of your hand off the tee on a par 5.
The front nine at Hunter Ranch, but particularly the first 6 holes I think are excellent. Both HR and LP enjoy rural wine-country type settings.
LP is the more difficult of the courses.
This being said, I do NOT think it's worth a special trip to play if the greens are punched to hell. Not that the greens are of any particular interest, but I don't believe the design is unique enough to "study". When consideirng LP or HR, you should be looking at which round of golf you'll enjoy more, as neither really merits a design study, and I think between the two you will probably enjoy the one that's in better shape a bit more - they're that close.
Other courses north of LA of which some on here have espoused virtues include:
Ojai
Monarch Dunes
Soule Park
I've not played any of those.
Rustic is aerating their greens the first week in October - it's aeration season in So Cal.
The fairways and rough there are in less than good shape...but it's still a better design and much more fun than LaP or HR...just a good deal further south.