In my experience, Park Hyatt is significantly more luxurious than JW. The hotels are smaller and more intimate, giving superb service. Further, during Hyatt's recurring Faster Free Night promo, I can make two inexpensive stays at any of the Hyatt brands and redeem at Park Hyatts. This gives me an effective rate of perhaps $150 for a truly luxurious hotel experience at places such as Park Hyatt Tokyo or Hyatt Vendome Paris.
Regardless, it's nice to have choices with our hotel points.