Last Fall I was out riding my '84 Schwinn Peloton with DT indexed DuraAce, met up with a younger guy on a Cannondale with all the disk brakes & such. He complimented me on my bike, I hung on his wheel for a couple of miles until we got to a stop light and split off. 40+ yr old bike with 60+ yr old rider couldn't really keep up with 40 yr old rider on a new bike for any length of time

Hills and more gears, brifter bikes are faster, but for me, it's 0.1-0.2 mph, and on any given day I might actually be faster on my old bike- but I have to work harder at it. I have a flatter route for my vintage rides, and for hillier, faster, or longer rides, it's my modern steel with 10 spd Ultegra, carbon wheels, etc.