Only the US 996S had ohlins forks as standard - but this model had a totally different engine for US emissions.
The forks on Euro S models are all Showa with TiN coated tubes. The main difference is the S is a Bip (dual seat) and the SPS is a mono (single seat). The SPS has all the extra trick parts mentioned above although I was told that some S models got ti conrods as they couldn't be bothered to create S engines.
The SPS will have an extra desirability that most ducatisti will appreciate. The S has dual seat and a lower price tag. If you want an exclusive Ducati get an SPS.
Both you will enjoy more than whatever you are currently riding