Agree with most above. Gasoline is best on models over 10 lbs. Has less to do with wingspan than overall weight. But the engines for gas are getting smaller all the time. Most gassers are two stroke and need an Amsoil or similar mix, just like a weedwacket or chainsaw. Still a lot cheaper than glow (especially at the volumes they suck down in large sizes). Some have electronic igniition and need a seperate dedicated sparkplug/ignition battery and circuit. Because of the spark and accompanying EMI they require a little more thought and care in where your servos and receiver can be located. The reward is that you don't need to diddle around with a seperate hand-held electric starter, flieldbox battery or glow driver. Radio switches on, prime and choke the carb, ignition switch on, put on a leather glove and flip the prop by hand. And the sound is right.

In the alcohol glow fuel two and four strokes the fuel is basically the same - alcohol, some percentage nitromethane instead of methanol and castor oil or synthetic oil as a lubricant. $17 to $20 per gallon hereabouts. Gasoline may catch up at the present rate!