I can't help but notice the coincidence that its Bill and Ted who are arguing that Pre-78 bikes are good Evo bikes... Sounds like a Bogus Journey to me...
The rider is the single biggest determining factor for sure, but any given rider will go faster on the better bike. And on the majority of tracks we ride in 2014, the 1979/80 models have a clear advantage over (standard) 1977/78 models.
Anyone who thinks a 1970s 125 motor is even close to a 2000+ one, clearly hasn't ridden at least one of the bikes they're talking about. The old bikes give away at least 20% peak power, and are far peakier - and unlike the Evo-era 500s, most riders will be able to hold a 125 pinned at least a couple of times per lap, so everyone can feel/appreciate the difference.
Sorry for the rant, but jeez...