FWIW, I chose to power my little inflatable "dinghy in a bag" with an electric trolling motor. Everyone has tradeoffs to make on their specific boat and motoring needs. In my case, I had no place secure to keep a gas powered moter except in the cabin, and I did not want gasoline down there. The electric trolling motor and battery both store safety down below (as does the dinghy when it's deflated). Also I'm cheap, and found the trolling motor for $80 and already have a couple spare group 24 batteries in my basement for driving sump pumps and starting my Trophy boat during the 1-2 weeks a year that I use it on vacation. This dinghy will get very infrequent use (once or twice a year), so for <$200 total it will have to be good enough for me. If I were a serious cruiser with a larger boat I'd get a more serious dinghy and outboard.
In addition, for the inflatable that I have, even though it's rated for 2.5 HP outboard with the motor mount, I felt it was safer to have the weight of the battery contained within the boat itself instead of the weight+torque of an outboard hanging off the transom. A steady 30 lb thrust should be enough to get this lightweight boat most anywhere in protected waters, and won't cause the flotation tubes to collapse under the pressure.
Weather lately has been terrible, so I've had to work in between rainstorms. All I've been able to do so far is attach the registration numbers to the boat (each one had to be attached with Krazy Glue because they didn't want to stick to the fabric) and install the motor mount. I hope to test it all out this weekend.