It really depends on the person's preferences and taste. Do you want to take a generator, chargers and several battery packs to the field or just a can of fuel and a starter box? Some won't want to deal with a nitro motor since you can't just set the needle and forget it like you can on a gas engine. As far as overheating, it's not something you need to worry about on a trainer. As long as the cylinder is in the airflow, it will never overheat. That said, an engine does require rebuilding after so much run time as bearing/bushings do wear and pistons and sleeves do lose their tight fit over time. How you take care of an engine will directly affect it's life between rebuilds. Obviously, if you crash an engine, it would need to be checked out before running it again as cranks do bend and can break. Then again, an electric motor's shaft can bend just as easily as that on a nitro motor.
Something else to think about is the noise factor. If you plan to fly at a local ball field, for example, people that live close by might not appreciate the noise of a nitro motor while an electric powered plane might not even be noticed