I have stayed at both and perfer Portofino Bay. It is a lovely hotel and our room was beautiful (deluxe pool view). I liked that is quiet and relaxing after a day at the parks.
I know you didn't ask about Royal Pcific, but I just returned Wednesday from a visit to Royal Pacific and I loved that hotel also. I really liked the tropical feel of this resort and it was very easy to navigate. Our room was quite nice and we had a dead center view of The Hulk and the nightly fireworks.
If you are looking for a large, luxurious room with a big bathroom, then stay at Portofino. The Hard Rock Hotel is very nice, but not as relaxing as the others.
My recommendation is either Portofino or Royal Pacific.