Problem is that flooring is nailed in the grooves on the side of each board (or glued, depending on each kind) while decking is nailed or screwed on the face of each board. One would have to be extremely careful not to damage the sanding maching disk if one were to engage a screw or nail head.
Having said that, I've used the large (16 inch) orbital sander one can rent from a DIY store here in the U.S. and used medium grit sandpaper disks. Works well, but for the best results, power wash the deck, rinse with common bleach (to get rid of the mold between the boards) rinse again and let dry for a day or two in the bright sun. The grains of the wood will rise as it dries and you'll get a smoother finish when you complete the sanding process. Be sure to sweep thoroughly before applying new finish...
You might want to consider an electric belt sanderf or those areas you can't reach with larger orbital sander...