If you are in poor health, get a snow thrower, otherwise use a shovel. 500 sq ft is not much area. So I would get a small snow thrower if any at all. Now for your self-explanitory questions. Basically, the larger impeller lets you handle deeper snowfall, The width determines how wide of a track it will do, electric start means you can press a button to start it. Most people that I have known who have bought these things let them sit all summer long with stale gas in them. Then when it snows, I have my driveway shoveled in less time than they spend trying to start their gunked-up snow thrower. Also, if you have a stone driveway you cannot use a snow thrower!