those are the worst times I have ever seen except for a few road and track times! If you are going to buy into "these" magazine stats at least go look at some numbers from Motor Trend. Go pick up an old motor trend, early 90's and the Z ranges 0-60 from 5-5.5s and finishes the quarter mile in 13.5-13.7s. The mitsu always comes behind. As for the Supra, according to magazine drivers with not much experience behind the wheel of these particular cars, have managed to better the Z's 0-60 by a few tenths and beat the Z in the 1/4 mile by a tenth or two in these Motor Trend tests. The cars are the same, Supra is easier to launch. If done correctly, a Z can do it, but thats not easy for normal drivers to do.
All I have to say is go race a Mitsu, I think you'll be pleasantly suprised.