The February 2011 issue of
Scoot Magazine has a pretty nice little story on p29 comparing the dyno results of a carbureted Vespa LX150 vs a factory injected LX150. I have asked their permission to reproduce the story. In the mean time, their dyno chart shows that the carb Vespa puts out more power all the way thru the curve, maxing out at 6.8 hp vs 6.42 hp for the injected version.
The article suggests that the injected LX150 burns less gas. Of course it would burn less gas. It produces less horsepower. It better complies with governmental regulations. It also costs $300 more.
Besides better performance at various altitudes, I have since discovered that EFI units are not affected by the wretched American gas that clogs tiny orifices. That could be good if you don't ride much.
Still... 6.8 hp is better than 6.42 hp.
If I get permission to show you their graph, I will post it.
Craig