In your shoes I would stick with the early car. They are wonderful things to drive IMO with the lack of weight really aiding the driving experience and aiding that classic feel.
Drive an S and see what you think though

. I wonder how much the cam timing is within spec on most Ss out there. Sure they may never possess the low down grunt of the S2s, but that's not to say they can be a total loss. On many moderns it has surprised me what a difference it can make, even on cars as feeble as a Clio 1.5 DCi, where it seems to make a world of difference the overall drivability.
Surely they must/be almost on a par regarding the low down pull when compared to a 951, which is semi flat before 3k (in 250 form) (OK it will move, but not in a hurry like an S2)!