I've been to the PCC luau, but not to Aulani's.
The PCC luau is like two shows in one. There's the dinner portion, which, obviously includes the food. We did the regular luau buffet (not the one with prime rib). I was pleased with the food quality and variety--and there are options for those who might not be so sure about the traditional Hawaiian offerings, but we were there for the pig, and it was delicious! While you eat, there is a rotating set of entertainers that come in and performs--various styles of hula, fire dancers, musicians and so on. Totally met my expectations for what luau entertainment should be. Then, later in the evening, there is a Broadway-style show in a large theater. This show was great, but it is also very different from a traditional luau offering.
The thing I really like about the PCC is the luau and nighttime show feature multiple Polynesian islands, not just Hawaii. The exhibits and displays are great--and many (if not all) of the young people working there are from the islands where they are working the displays (as in, the people working the Tonga section are from Tonga). And we really did like the evening show--it was far more than we expected from a luau and all of us enjoyed it a great deal.
It may be important to know that because the PCC is operated by the LDS Church (Mormons), there is no alcohol served at the luau.
The only other con I can think of is the distance from Aulani. It's a drive, for sure. I would plan to spend a good portion of the day at the PCC, rather than just heading over for the evening, for sure.