A gas-powered lawn mower offers several benefits over an electric one. For example, the increased power allows them to easily cut through longer/tougher grass, and they are not limited by cord length or how long the battery lasts.
Sometimes it can be hard to start gas-powered lawn mowers, but with an electric starter you can be guaranteed of it starting first time.
Cordless tools/machines are suited to a variety of different situations, as you are not limited to only working in places with power sources nearby.
A self-propelled lawn mower requires less effort from the user, as you don’t have to manually push it forward.
The mower can discharge the cut grass to the side. The cut grass helps to fertilise the lawn and helps preserve moisture in the summer, and means that you do not have to empty a grass bag/box. However, this is not as effective as a mulching lawn mower.
A self-propelled lawn mower which is faster allows you to cut your lawn in less time, as it is quicker to make each pass.