Personally I prefer to download all songs with DD, though not for me, as I crank up the song to 100% as soon as I start it. However when I play multiplayer, it's nice to have the option for my friends to be able to play it however they prefer. Some people don't like missing the notes and not being able to keep up, so no DD would be frustrating for them. Some people don't mind if they miss some notes but hate not being able to see all the notes that are actually being played, so playing with DD is a pain, but at least you can crank the DD to 100%. Can't do the opposite. So... in short... I always download DD when available, even if it's a pain for me to have to manually adjust them to 100% on my first playthru.