RE: GAS ENGINE OR GLOW???
The problem, of course, is the size of engines in glow vs. gas. The most obvious observation is that the gas engines are larger and power larger aircraft. There are some smaller gas engines, but I'm not sure what ones would be usable in something that uses a 60 size glow engine.
If you are looking to build larger aircraft, then certainly gas would be a consideration. But for smaller size aircraft, I don't think there is a compatible engine that would replace a 60 Glow.
The benefits are obvious. I just saw that gas at the local station (on the way to work this morning) was $1.54/gallon. That makes it pretty obvious a choice as compared to $12.00 (or more) for glow fuel. But, as mentioned above, finding a gas engine to replace a 60 glow may be a problem. Also, the gassers are somewhat cleaner.. no oil on the wing/fuselage/tail feathers.. is one advangage of gas over glow.
CGr.