years back while assisting with a field repair a crusty mechanic asked me to hand him a large wrench. When I asked him to specify a size he said it didn't matter as he was going to use it as a hammer. Probably not the first time this was ever uttered, but new to my youthful ears. The difference of ten mph means nothing.
buy a capable bike, then to satisfy your curiosity buy the antique your grandpa rode. You will have true satisfaction using each within their realm of capabilities. There is no way my bullet will ever compare in performance and handing to my KLX Kawasaki, Grandpa would have loved to experience the Kaw. Just as I have enjoyed the experience of riding his bike. This is a simple concept, the motorcycle evolved over time into our modern day bikes. It has been done, is now complete and with excellent results. pumping money into an antiquated machine to gain performance will not satisfy the "daily rider". Read Vince, then , Read Vince again.
It is a wonderful feeling to wake up with options. Some days I'm the grouchy old fart content to hammer away with a twelve inch Crescent, others I gracefully wield a set of polished spanners.