That question is bound to head in the same direction as "which is better" about the same subject. One of the half-dozen perennial emotional circular 'arguments'.

The "diference" is that gas planes are powerd by internal combustion engines deriving their power from a conventional liquid fuel as it's energy source, and electrics are powered by electric motors sourcing their energy from an onboard storage battery.

Most RC fliers will be influenced by or biased toward whichever one captures and excites their imagination to most interest them than any logical aspect of the pros and cons of operation. That's the one for YOU to buy/play with/clique you will most happily fit in with.