I've been to both places (once, both in the same week

) and for the better beach, you want the PCV.
The snorkelling is better hands down at the PCV. If you go over by the scuba dock, there is a small reef that you can snorkel that has lots of fish.
There is plenty of shade at both places, so it's not a morning race for a shady spot.
The beach at the PCV is longer as well, but you could still walk the whole length in about 20 min. If you like to walk in the water, water shoes are reccomended, as there are some rocky spots.
The swimming is better at the PCV as well, because the GPT beach is very shallow, for a long way out. There was also a lot of sea grass when we were there last, but I hear they have cleaned it up a bit.
There are 3 beach bars, on the PCV beach (Pesquero, PCV, and Blau) but the staff is happy to give you a drink, even if you are from one of the other hotels. I always get juice at the Blau beach bar, on my way to the dive shop.
I'll go thru my pictures, and post some, so you can see for yourself.