1200 S is the best sportster you can buy (imho). Dual plugs, higher compression, dual discs up front, among other things. How many miles on it and what has already been done to it? A/C, head breathers, exhaust, motor work? Bone stock? What's the mileage look like?
In any case, looking at prices for both right now, I'd say if the sporty is in good condition you literally stealing it from the guy. Just my .02.