At the Pit of Carkoon, two changes:
- Jabba falls into the Sarlaac
- Leia strangles Boba Fett with her chain
It just makes sense to me that having this bloated slug fall into the ravening hole in the desert would make for an awesome moment. Plus, you get the symmetry of the villain who likes to feed victims to monsters (the Rancor, the Sarlaac) getting a taste of his own medicine.
And, by having Fett die at Leia's hand, the baddest bounty hunter in the galaxy no longer dies by accident. He's eliminated by a resourceful and deadly foe, not by the SW equivalent of slipping in the bathtub.