No surprise. You forgot to specify other variables such as driver skill, tires, suspension tune, engine power, weight, etc.
Seriously, given that driver skill was similiar and that both cars had similiar power, weight, suspension performance and tires, the RWD is always faster, given that none of them are seriously overpowered or underpowered. All else equal, RWD wins hands down. Maybe that friend of yours just spent some major $$ on a Koni coilover kit?
Anyway, the RX7 isn't that fast or powerful vs the newer cars anyway whilst in stock form. A well driven and tuned new Type R can easily beat any stock RX-7 (again assuming both drivers are highly skilled).
Well, at least until the front tires die.