Off hand I'd say the majority prefers physical media, for reasons including, taking the game to a friend's house, having a larger collection of games on the shelf, resale value and my personal favorite: reading the game manual while sitting on the can.
Add to that the extra video that is on the BR-D, for those who care about those little extras. It's not on the download since that would make the 1.8GB download considerably larger, especially if the video is in 720p or 1080p resolution.
The upside of the download is most likely faster load speeds when reading from the HDD as opposed to the optical drive. Someone with access to both should do a comparison.
And of course, instant gratification for the gamers who don't live 5 minutes away from a game retailer and who aren't the kind who visit regularly for new releases even when they already know full well there aren't any scheduled for that day.
