I would say that it is not the bike frame that you are comparing but the components as well. I can easily imagine one frame competing against another. I cannot imagine a downtube friction shifter competing with today's indexed brifters. Nor can I imagine the braking efficiency or control being the same. You have to admit that it is a lot easier to keep your hands on the bars, shift right to the correct gear and lock it in. Now try that same thing with downtube friction levers. There has to be a difference. You don't need to wish for a head to head race. How are the records holding up for the same races on the same routes, etc.