All I can say is the reason SPF is higher is a lot of options for the Backdraft are standard on the SPF. Take the Backdraft price and then add knock off wheels, top and side curtins, heater,
oil cooler and a few other items and then compare prices.
Then look at the re-sale price down the line. Backdraft makes a fine car but the SPF is just a little bit nicer.
Just my humble opinion.
Mark