I have stayed at both and while I love the Polynesian's location, we loved AKL so much that we bought into DVC in order to own at AKV.
Regarding guests from other hotels using the Volcano pool - I agree that some sort of wrist band system needs to be instituted because of the size of the pool and its convenient location. Since we are DVC members, we are permitted to pool-hop by Disney (except to AKL and BC) and we have used the Polynesian's pool after a morning at MK. That may or may not have been the case that was reported earlier on this thread. Hard to tell, therefore a system like at SAB should be considered.
I would say that the difference in price between the two resorts reflects more on location and size of room than in quality of the resort and amenities.