ORIGINAL: IXLR8
The gas engine with ignition and a battery will weigh more but the best way to mitigate that is to reduce your tank size. Liquid is heavy and reducing 6-8 fliud ounces will make up for a lot of the additional weight of the engine.
This is true but as the flight progresses the weight advantage becomes less & less. I have 26cc, 40cc & 50cc gassers and am finding it very difficult to see any advantages to gas under 50cc other than somewhat cheaper to operate and if I was that strapped for cash I would find another hobby. Again my .02 worth.