Those sets came out a few years ago and are no doubt being reissued for the Christmas (yes, it's already that time again) season. Both are battery powered. The lower priced set has the original SR cars. The more expensive set has different, more "funky" cars, possibly from the movie (which I did not see).waitaminnit... they make TWO of those sets? with different cars, even?
They have to operate on a lower voltage because 4 D batteries are only going to get you 6 volts. I'd never run them on batteries. It would be much less expensive to get a Tyco/Mattel wall wart and one of the Router Speed Controls from Harbor Freight (under $20) so you can dial down the voltage.I did notice (thru experience) that the battery operated sets seem to operate on a lower voltage, the kid can keep the cars on the track tons better, but batteries die out fast.