Just on the engines alone, the 155 version has 12.1kw @8750rpm / 15nm @ 6500rpm
The 125 version has 11kw @9000rpm / 12nm @ 6500rpm.

They are a lot heavier though, so i think the Yamaha's would still win a drag race based on power to weight, but these Piaggio's are fully loaded with everything including ABS / Stop Start / LCD Dash etc etc. They are well engineered and high in quality too.

You can't beat the Aerox MotoGP bike styling, but if Aprilia did a scooter like the Aerox with the Piaggio 155 engine they have (Piaggio own Aprilia), then that really would be a competitor to the mighty Aerox.