There’s not really a best sander for working with wood, but if you’re regularly working with or restoring furniture, the sander that you’ll get the most mileage out of is a palm or hand sander. Specifically, look for a detail sander that has a pointed edge, which is ideal for getting into difficult corners.
The smaller size and surface area of these types of sander gives you a lot more control and lets you get into the smaller areas that would be harder to reach with any other variety.
If you regularly work with cabinets, desks, tables or other surfaces that are large, flat planes, you might also want a belt sander, as they are the fastest way to strip and prepare big areas. Any imperfections and missed areas can be revisited later with another tool, or just touched up by hand.