Gas:
+ engine and kits are cheap / fast / goes far / gas is cheap / easy to fix
- Loud / only legal in around 20 states or less / broken engine may required
whole New engine / may have to mix gas and oil / storage of gas or bike
Need to be somewhat mechanically inclined to install and maintain
Electric:
+ may not need to be fixed/ quiet / if its not legal,you can't hear it running
- may cost more / slower / less distance /replace batteries often/ charging
Easier to install and maintain,may even come already on bike
I had both, the gas went faster,cheap,reliable,unlimited range,loud;
the electric was slower,free to power,short distance, but quiet.
If you spend enough on electric parts, you will have better speed and distance,atleast you won't get tickets for a loud muffler. But if its legal in your state,have a place to store bike and gas and you're handy go for a gas kit, if not go for a electric one.