If you're picturing an orbital sander to involve a large, rotating sheet of sandpaper, you may be mistakenly thinking of a floor polisher or buffer. An orbital floor sander does not move in circles. Rather, it's more like a vibrating sander, making short "orbits" as frequent as 3450 orbits per minute.
Orbital floor sanders are heavy to pick up. But once they are switched on, they glide effortlessly across your floor.
You won't be able to plane down imperfections in your hardwood floor, as you might do with a drum sander. Then again, you cannot accidentally gouge deep valleys into your flooring, as drum sanders can do.