I have both. I bought SHIII first and I got hooked for two weeks but then when I got DW and I started playing it, I didn't come back. The feature I like in DW is the fact that you play multi-station, that is, two or more players on the same platform (sub, FFG, Orion and helo) manning different stations (sonar, radar, acustics, etc...)...
Definately, SHII is the best in WWII sub simulation and DW is the best in modern warfare simulation...
