What year is your friend's Supra? Even if it's the last US production year, that makes it at least 10 years old. Any sportscar that old will eventually run into problems, and that's not factoring in how your friend drove/treated the car.
I owned a '95 MR2 Turbo for 4 years and did a lot of speeding/commuting (40 miles from the San Fernando Valley to Long Beach one way and then back again 8 hours later, 5 days a week), plus canyon runs (specifically Mullholland) on the weekends and had no problems whatsoever. Did you buy your MR2 used?
And concerning Toyota's V6s, the IS350's V6 (a sports sedan, not a pure sportscar mind you) has more power/torque than the Acura NSX and Infinity G35/Nissan 350Z (which are, with the exception of the G35, pure sportscars). I'm sorry but I don't know which competitors you are talking about posting bigger numbers (unless you're going across the Atlantic to Europe).
I suppose we'll just have to agree to disagree when it comes to the Big T.