[Smaug]

If it's about power:weight, you need to be looking at motorcycles, not scooters. Several now by Honda and Yamaha are available with dual-clutch automatic transmissions and have power:weight that just blows away any scooter. Some of the Honda ones (CTX) didn't sell well and are now a couple years old, new, sitting in the dealerships, and marked down $3k.

To me, scooters are about convenience and utility, I've had Japanese scooters from 49cc to 582cc. Singles and twins, air and liquid-cooled.

Also, there's more to power:weight than HP. Torque is important too, esp. on something heavy for its engine size, like a scooter.

Lastly, don't buy BMW unless you want to be nickel-and-dimed to death with service and parts costs. Their build quality is good, but they need more maintenance than the Japanese bikes, and it is expensive maintenance.

Stick with your Piaggio BV; that's a GREAT bike. If anything, upgrade to a nice used BV350. They are very quick and have a better seat and windshield than the 250s.