I find the one at the Lava Pool small and often crowded - it’s not my favorite place at Poly. The setting is nice with a drip/infinity edge facing the Seven Seas Lagoon/GF.
The one at the Oasis Pool is much larger and more properly sized for a resort the size of Poly. You can share with others and not be all up in their business. It can be busy too, but often not as busy as the Lava Pool. If we want to use a hot tub, the one at the Oasis Pool is our first and only choice, in our humble opinion.