I'll post a summary of the results of my testing.
Although I still won't use them, my testing revealed the RX-7 LM and Pitwork Z as still being too fast.I may have simply gotten better laps with them than I did with the NSXes or the GT-R, but they were significantly faster than any of those. In contrast, the Supras were really slow, and definitely not competitive with the rest of the cars. But again, maybe I just didn't spend enough time on them and got a poor result because of that. The GT-R is definitely being solidified as my choice, though, because it will probably be better in a long race than either NSX would be. The Takata NSX is definitely starting to look worse the longer I test it.
In GT300, the MR-S and the Garaiya are very close; I thought that the necessity of short-shifting the MR-S might have escaped the testers, making it too fast. I think that consistency will come more easily in the Garaiya, though, and it's nicer to drive, so I'll stick to it. The S2000 just didn't seem on par with either one, and the RX-7 was closer, but still significantly off. While the Subaru and the Celica had nice handling, they seemed not to do very well at high speeds compared to the MR-S and Garaiya.
