Go with the orbital. No question. If the wood is cupped or uneven then start with the coarsest grit paper they have and work up from there.
You'll need a hand held sander to get all the way to the edges, but the orbital will get pretty close.
Most of the floors in my house were done by pros with drum sanders before I bought the house. There are marks and gouges all over them. I did the living room myself with a Home Depot orbital. It is absolutely flawless. You almost can't screw it up with the orbital.
How long did it take? Forty hours or sanding! Yeah, a drum sander would have taken two hours, but it wouldn't look as nice. When you're working on a 50 year old oak floor, it's worth the effort.