The ST is no where near as capable as an s2000, the s2000 would eat it for breakfast (both as stock).
However, the ST would be a lot more comfortable, with more creature comforts and a lot more practical, and yes I have owned the ST for 2 1/2 years, and currently own an s2000.
I would imagine standard for standard the S2k would despatch it quite easily
I bet the S2000 feels like that because it is a lot more connected, fun and generally more 'raw'. But having spent an evening blasting around with an S2K, I can assure you that on the road, it doesn't really have anything over the ST in terms of outright performance.
Admittedly mine isn't exactly standard, but all out power doesn't mean much on what is mostly b-roads over here, and if you spent the same amount modifying an S2000 as I have my ST the results would still be the same.