Not likely 35mm. But why 35mm? APS-C came and looks like it's going to stay. Any of your clients says that they'll only take 35mm digital shots? I see most people here taking APS-C shots of equivalent if not better quality than some medium format shooters!
As for S3 vs D200, for easy JPEG results, punchy colours and good dynamic range, S3. for faster cam, better build, and newer technology, D200.