We've done both resorts and both are good choices.
They have two different feels to them.
We love the Poly because of its themeing and the nightly torch ceremony . . .the tropical feel that you are on an island, the smell of the GCH, the Kona Cafe and the awesome Tonga Toast, the very nice CM's, the beautiful views, going around saying "Aloha" all day long, everyone is your "cousin".
We love the Grand Floridian because of its grounds, the romance of it, the brightness, the feel that you are in a magical place, mousekeeping is excellent, nightly turndown service, 1900 Park Fare is an awesome place for b-fast, walking to Gasparilla's and getting a refill and sitting watching the fireworks by the Marina.
I really don't have any cons for these two resorts . . .I do like staying at both of them, a little more at the Poly though, my kids really found the Poly to be their favorite.
We are heading back to GF this July 4th and we are very excited about it!
I would switch back and forth . . .you did the Poly, now try the GF, otherwise you'll never know if you'll like something if you don't try it.