Yes 1/10th the MF but unfortunately the same closing costs.
Your options for buying:
1. The cheapest option (cost + MF)
2. The easiest option (the first that comes available)
3. The resort you want to use (Aulani)
4. Another resort you might use (VGC? Since you're in CA)
5. Another highly desirable resort (BLT, Beach Club)
Any of them would work initially. Once Aulani sells out, the Aulani ownership option would essentially guarantee that with advance planning you can get the dates you need. It would be the most expensive option, but since you will be trying to marry two TS stays, it's worth considering so that you are not out of luck down the road (although you could just sell the 25 point contract if that happened). You'd have to run the numbers and see what makes more sense for your circumstance.
We like the Hilton Head contract in theory because we mostly want to travel to theme park resorts in super-off-season (to avoid crowds). But Hilton Head we want in prime season. But I say "in theory" because we've never actually been to Hilton Head. But if you are needing a prime season, it's more of a continual sure thing to own there.
It might take you a long time to find a 25 point Aulani contract, though. I'm not sure there will be many out there since the points requirements are so high. Owning Aulani might be impractical at that point level.
H