you might end up doing worse on the MCAT the second time around. then what are you gonna do. reapply to your state school? that would be an awkward interview
....if you're really unsure, let someone else who's begging for a chance have at your spot..... seriously, are you kidding me? take the acceptance and GO!!! Who knows what will happen in the next app cycle?
Most schools won't know whether you applied to med school the previous year provided that you didn't apply to THEM. Though I am not a reapplicant, I did notice some secondary applications this year that did ask if you applied to ANY other schools in previous years. Just FYI.