I am building an RCR, and I seriously considered a SPF. I think the previous comments here are spot on.
The SPF is much more a replica and is meant to be very, very close to the original. Since it is a rolling chassis, the quality is very high but you only have a limited number of options. The drivetrain is more limited but is original (Ford motor, many are sourced from Roush). Understand that the only transaxle is going to be the ZF or an equivalent (such as the newly designed ZFQ from quaife or the RBT). These can be very hard to source and have delayed cars, sometimes near to two years. As mentioned, it is VERY important to have someone who knows what they are doing complete the drivetrain installation. Olthoff is one of the best, and you'd be silly to go anywhere else if you are on the east coast.
I ultimately went with the RCR for two main reasons: I wanted a more modern car and I wanted much more flexibility in my options. The body is a Mark I, with molds taken directly off an original. At that point, originality pretty much goes out the window. It is an aluminum mono, with billet aluminum suspension arms, modern geometry, double adjustable QA1 shocks, Wilwood race brakes with Nascar rotors, and a unique drivetrain. I wanted a readily available bullet-proof transaxle, so I went with the Ricardo that you know and love. I am mating that to an LS7, partly because the GM block is short enough to let the Ricardo fit, and partly because it is a crate motor with all the boxes checked (all aluminum, dry sump, Ti rods, Ti valves, 7k rpms, 500+ hp, near to 500 ft/lbs).
RCR will do and has done turn-key cars. You will lose some originality and you will not have a continuation VIN (which is purely marketing if you ask me). But the options are much more varied and the car is less expensive (probably about 20k less).