Depends on what you're after. All three varying platforms with differing offerings. For performance or track I'd say M2 over the rest, and if you want reliability and semi Jap I'd say the Supra. The RCF is like the entire F range, slower than modern cars, heavier, reliable and cruisers. Sure you can start making them lighter, tweeking them, but they'll never have the support of say the M2 and Supra. Which is where the final key reason for why you'd have a Lexus F, exclusivity. With the GSF, RCF and ISF, you'll have something not many have, and it's also a reliable and relatively economical V8.
I'd say it's personal preference and what you plan to do with the car.