Depending upon what exactly you are comparing, a moped is much less expensive than a car or a motorcycle. They also get better gas mileage and cost less in insurance.
Since they also go much slower, it wouldn’t be a good fit if a person wants to drive on a highway or larger road that has a higher speed limit. In residential or business areas where the speed limit is around 30 mph, a moped would be a fine option for travel.
It all depends upon what it is being used for, how far it is to drive, what the weather is like (because there is no weather protection on a moped), and other similar scenarios.
Another thing to consider is parking. Mopeds can fit into much smaller parking spots, so you can often alleviate parking woes by driving one. Depending on your local laws, you may even be able to park at a bike rack, which could give you the closest parking spot you’ve even been able to score.