If you’re torn between needing an oscillating multi-tool and a rotary sander decide how much work you need to do with it. A rotary sander will cover a larger area and is more powerful than most multi-tools. This will allow you more power and usually a variable speed. These sanders work on the same principle of an oscillating tool where the head moves back and forth at high speed to create a smooth finish much the same as you would through hand sanding, only much quicker. A 5” tool is more than enough for most home use and will work on sanding wood and metal projects. The nicer ones also have dust bags so help make clean-up easier.