We have done the following:
DL express bus, works ok, especially if you are staying at the DLH as I believe it stops there first. may have to get off that bus onto another one if you are staying elsewhere, and you have to wait for it to arrive on it's schedule. My least favorite option.
Karmell shuttle, worked fine, again somewhat of a wait, even with ressies, but usually we were the only ones or one other group so not a lot of riding around other hotels.
Taxi, a little more expensive. We did this last year when there were three of us instead of two. Much more convient, as you just walk outside the airport and hop in. This year we will cab again even tho it is only 2 of us. Of note, we stayed at PP last year and when we were leaving I asked about a cab and they gave us a coupon for a flat rate going back to SNA.
Good luck