Which is better for deck flooring: 2x6 or 1x6 deck boards?
1X stock is fine if you have 16 inch on center joists, and the joists are themselves sized properly. Using 2X stock over undersized joists does help make the deck feel more solid. If you have 24 OC joists, I'd definitely stay with the 2X decking. An other option if you have wider joist spacing is to add a joist between each one if possible,  then you can use 1X wood or even better, composite decking that will last a very long time, low maintenance and you can have your choice of colors and not have to worry about staining etc.