Steamworks is win. You can buy the retail version and once it's linked to your account, be able to download it any time in the future. It's the best of both retail and DD.
Though I suppose it'd suck if I ever wind up in a situation without a reliable internet connection.
Edit:
Though I'd assume you'd still be able to play the game with the disc in even when offline? Then Steamworks would simply be an additional bonus, letting you redownload the game should you have issues with the disc.







