I think a lot of the various preferences are psycological, based on what we started out riding and what we feel comfortable on. In reality, all of the SOHC fours are very similar. A friend bought a "new" (left over) 550 four back in 1979 when I had my 750 Kawasaki. He had two more cylinders than I, but I could outrun him ever so slightly. I was impressed by his bike. Before that, the dealers had me convinced that I did not want anything smaller than a 750 for two up riding. Later it was obvious the 550 would have done fine, but by then I had my 750 and the mold was set. I prefer a larger engine for the torque to haul my fat a$$ around, although a smaller, lighter bike might do as well, since it's all about power to weight.
Yes, there are plenty of smaller displacement bikes out there with more power than I have now, but they are typically physically smaller. I have looked at and sat on a new Kawasaki Concours, and even though it's 1000 cc's, the bike feels too small. OTOH, my old K75 (a 750) BMW had all the room in the world. Once again, this all goes back to my initial perceptions when I started riding in 1979. I'm just glad I didn't start out on a full dress Harley!
