It’s been several decades since I bought a wood sander, but I recently needed a new one for a large finishing job. I was pleasantly surprised by the technological advances now standardly available in inexpensive sanders.
There are three key innovations here: “random” sanding patterns, using sandpaper disks that attach via a velcro-like surface, and a vacuum that works through holes in the paper. Together these three features produce a much superior machine to the simple vibrating sander I had before. Random-orbital sanders spin as circles within circles, leaving little discernible pattern of abrasion on the work. The round hook-and-loop paper is magic. These disks securely attachment and detach in a second, and don’t slip. This quickness encourages you to instantly change to the appropriate grit size without hesitation. Lastly, sanding produces massive amounts of dust, and the mini vacuums really decrease the volume of stuff flying around. The debris is sucked into a small cloth bag that doesn’t interfere much with work.
All these features and more are available in higher end machines, but also in cheaper ones as well. I’ve been using a Dewalt, D26451K which is an entry model at about $55 street price. With a coarse grit paper, its 3-amp motor will eat wood if you need to, but it is light enough to feather touch a fine grit. It takes the standard 8-hole hook-and-loop disk. Many companies make these disks in all possible grades, varieties and types. Although they seem expensive, I found these disks lasted longer than the pieces I used to cut from standard sheets for my old machine. The small dust bag is sufficient for most weekend projects, but may seem small if you are sanding whole walls; you just have to empty it more often.
None of these features may be new to most woodworkers, but I have not been paying attention; I wish I had got one of these years ago.