A 250 or a 400 is more than enough for the roads. They're more rewarding because you can use all the revs and gears, and they're more nimble in corners. Easier to park, cheaper to run...so many advantages. But not comfy on the motorway or a long journey, and not great for luggage and passengers.
Maybe I look for a bike that isn't fast at all. The equivalent a BMW 2002. Enjoyable for totally different reasons.