Hi, I'll take a stab at this since no one else has responded. We stayed at the Sunspree years ago (I'm thinking 6 years ago) and we thought it was a bit run-down then. The pool area was fine, but the rooms looked like they had taken regular, large Holiday Inn rooms and stuck a kidsuite in the front up by the windows. As a result, I felt the adult area was dark back behind there. Our room had a problem with damp carpet too, that never dried during our 2 night stay. On the plus side, the theming of the kidsuites was very cute.
We stayed at HIFS twice about 4-5 years ago. The kidsuite we had was unthemed, but I would definitely pick HIFS over the Sunspree. The breakfast is adequate, and although we found the rooms already showing their age a bit, we had much more room, the rooms were brighter and we like the pool better.
So if you can get the Sunspree for a lot cheaper than HIFS, it might be worth it, but I'd switch to HIFS.