How many shops did you visit before you got this bike? I'm concerned that the salesperson automatically assumed that a SS would give you a better work out and that they didn't do a proper fit for you. The best workout will come from the bike you ride the most. At this point it doesn't have much to do with the drivetrain. If you ride the hell out of the SS, it will be awesome for you. If you don't ride because it's a pain in the ass to get up the hills, then think about selling it and getting something else. But thats getting ahead of the question.
You might want to call around to see if any shops in your area will do a basic fit (measuring your body to get the proper saddle height and saddle-handlebar reach) for $20-30. Usually shops that use the Body Scanning system will do it for about that price. Like they said above, standover doesn't have a whole lot to do with proper bike fit. Maybe check back with the shop you bought it from. Just because one salesperson didn't didn't really know what they were doing, it doesn't mean that the shop is bunk.