Well, those two bikes have different intended uses. I think the STP is meant to be a heavy duty bike for jumping/urban and some trail riding (like the spesh P.bikes and kona jumpers), the Trek is just an entry level XC bike. The Trek has a better rear derailleur, but other than that, the STP definitely has better stuff. Better fork, real cranks, strong(and heavy) rims on disc hubs. But if you're going to be mostly doing XC/trail riding, the STP may not be the ideal bike.
If it was me, I would keep the STP. If after riding a few months, I decided I wanted a more XCish bike, I would take the money I'd been squirrelin' away for a few months and go get an XC bike(better one than the Trek), and keep the STP as a play bike.
