Quite simply the older drivers are better optimised for the workload that goes with that game.
The 10.1 drivers i would guess are pretty specifically targeting getting the best performance from 5 series cards. Thats what usually happens, past 8.12 i didnt see any need to update for my 3850.
Im running 9.11 Drivers on my 4770, that seemed to be the point where the upgrade just didnt seem worth it.
Its always a good idea to read the release notes and see what and where the improvements are before updating Tweaktown are pretty good at reviewing the drivers.