I use an S2 constantly. It is a nice, simple mechanical body that will mount the Carl Zeiss T* lenses. I love the CZ lenses but they are expensive and I already had an investment them and I like manual SLRs so the S2 was my only option except maybe an older Yashica.
If you are starting a system from scratch, it would be hard to overlook the superb quality and economy of the Olympus.
They are both excellent cameras but I think I might lean towards the Olympus. I can't imagine you being disappointed either way.