Dreams Cabo is a nicer resort than Dreams Puerto Vallarta in my opinion - having been to both. Cabo is more expensive for your guests though which is why we chose PV, I also loved my wedding coordinator in PV which was another reason.
I also like the town of Puerto Vallarta better, more authentic....unless I am just going to party and lay out by the pool, then I say Cabo! I love both places, but they are very different.