Pluses and minuses with either propulsion method. Dependent on the dinghy and how it is carried on the boat, you have to schlep the heavy battery back and forth on each use. If you're making a short run to shore, you don't have to carry extra fuel with the outboard. The battery has a finite power use capacity; a gas motor can run indefinitely, as long as you keep adding fuel. The electric is quiet compared to an outboard. If you are at anchor, you will be running the generator to charge the dinghy battery. Less of a concern if you usually stay in marinas and have power. No need to carry another fuel onboard with the electric.
If push came to shove (pun intended), you could hip tie the dinghy to your tug and move it (slowly) with an outboard on the dinghy. The electric is going to be hard pressed to serve the same duty, at least for any length of time.
Your use will determine which will work best for you.
Jim B.