Theres pros and cons for both, with the invention of small cheap(ish) cdi ignitions there is no reason you cant convert a glow engine to 2 stroke gas and it's quite popular to do so in some types of competition flying.
But there are other considerations such as some of the plastics and coverings that are used have been developed with glow fuel in mind and will deteriorate real quick with 2 stroke gas.
Runing 2 stroke gas tends to make the motor run hotter (due to the less lube) and some motors need a "special" liner and/or piston, with the electrics of the gas engine there are more problems with moisture.

So its realy horses for courses