The old bikes are more race oriented, on the track they will eat a modern 250/300. On the street, things might be a lot closer. A new Ninja 400 probably beats them all.
Yeah no....
My old 350LC in its flexyflyer frame is much faster than my R3, and the ninja 400 while faster than the r3....isnt 2 stroke 250/350 fast. The RGV250 and TZRs and NSRs are rocket ships. On the street you have to rev the piss out of them, and they arnt much fun. But an older RZ350 YPVS is a better street bike all around than the modern 300-400cc learners.
There is a reason the RZ350s and 250 2t bikes are forced to race with the 650 twins vs the 300s.