I plan to refinish the hardwood floors in three bedrooms using an orbital floor sander because they seem easier and safer for beginners than the drum sander. I need something to sand the edges, and I've wanted to buy a rotary/oscillating tool for a while. Which would help me more with this job? Or should I buy an actual hand sander instead?
Unless you love spending time on your knees, rent the drum sander and the rotary edge sander. If you are worried about losing control of the drum sander, start with fine grit while you are getting the hang of it. Or ask the rental place to leave the old paper on it. It is likely to be toothless enough that it will be very hard to do any damage.
Orbital sanders are very slow, and generally are used for furniture making.
Sanding produces enormous quantities of dust. This is one reason you want to get done quickly. Even if you put plastic over the doors and heating vents, dust gets everywhere.
It's a good idea to have someone working with a vacuum as you sand. Get it off the floor ASAP so the next pass with the sander doesn't cast it into the air again. You will probably want to wear dust masks.
I have three sanders right now. A 7" disk sander that I can also put cuttoff wheels and wire brushes on, a 3x21 belt sander, and a 4x5 orbital sander. All 3 get used regularly, but for a floor project it would be the belt sander that would be used the ost.