Depending on the size of the deck, you may be better off renting one of those hardwood floor sanders. It's got a large disk and it's something you can stand up to use. You can buy different sandpaper for it and then all you'd have to do is hand sand the corners.
I'd be careful with a belt sander. If your not careful you can make the decking wavy. A vibrating sander will usually do a much better job on a large flat surface like your deck.
I'd be careful with a belt sander. If your not careful you can make the decking wavy. A vibrating sander will usually do a much better job on a large flat surface like your deck.