A good floor sander can make patching experts out of the most novice of tennis court painters. The most skilled phase of tennis court repair and resurfacing is patching. Hiding patches so they can't be seen through the finished color-coating is a big part of that skill. Many professionals are able to hide their patches without sanding, although many others use a floor sander on every job. I always recommend mechanical sanding to my "Do-It-Yourself" tennis court painters. The rental cost of under $100.00 will pay for itself many time over in the quality of your finished surfacing project, the reduced wear and tear on your knees and hands, and your dramatically lower stress level. A floor sander can smooth and feather a patch in minutes that would take hours on your hands and knees with a mason's rubbing stone.
So your decision should not be if you are going to use a floor sander, but which floor sander is right for you and your tennis court repair (painting) project. There are three main types of floor sander that are readily available at your local rental store. If you have a Home Depot, with a rental department, nearby, you should find all three sander there. No matter which sander you choose, make sure you rent enough heavy extension cord to reach from your outlet to the farthest patch you plan to sand. Also, make sure to purchase the coarsest sand paper they have (12, 16, or 20 grit are best). Don't use 40 or 60 grit paper, they are too fine, and will likely polish your patches, causing the coatings to "slick off" as you squeegee over them. This means the coating won't grip to the patches, leaving shiny bare spots where very little paint is left behind.
The Three Types of Floor Sanders
The Drum Floor Sander
The Orbital Floor Sander