I intentionally did not try an S as I felt the 2001 Boxster base had sufficient power and slightly better fuel consumption. Mine had 30k on it 2 years ago when I bought it so the components like water pump, coolant reservoir, etc had less miles on them.
As the above poster says try both. Make sure the one you want has the options u want like manual vs. tiptronic, heated seats, psm etc. Of course you should try several and for sure get a PPI on it before you commit.
Enjoy the ride.