Depends what you want to do,

Gas engines are heavy, compared to electric motors and lithium batteries, so for modest endurance flights, electric works out better now, but for long endurance flights gas or diesel would be better.

Curtis youngblood demo'd a nitromethane powered quad as seen here

http://diydrones.com/profiles/blogs/curtis-youngblood-single...

I can't imagine anyone would use a nitro powered platform for any commercial use, the fuel is too expensive and the motors require too much maintenance.

I don't think we need autonomous machines flying around polluting (noise and chemical) spaces.