Hi Kapitain,
I play DW myself. Had the game a couple if weeks before SHIII arrive. Also have 688(i) and Sub Command. They are both great games. Though both are subsims they are very different from each other. I enjoy DW in that it's more like a very high tech game of chess. And SHIII ... well, i've always been a big WWII genre fan and the game does a lot to bring you back in time. Sitting at my computer listening to the WWII radio mod on the gramaphone really does a lot to immersion. It's both simply and more challenging to play at the same time. Simple because you have less to worry about in terms of sonar modelling, TMA, weapons platforms etc. and more challenging because of the nature of the war itself and cetain limitations of the old U Boats.
I recommend you go out and buy it as soon as possible
elcid