AOD DOS has variable pitch sounds for the diesel and electric motors. CAOD uses just a single sound track. CAOD allows you to aim the deck gun. I find the graphics better in AOD; more solid and well defined. CAOD seems to run at an inconsistance rate when it loses windows focus. AOD does not have this problem. CAOD includes a lot of extras like an online manual and interviews with 8 u-boat commanders. That's why I installed it; to watch them.
This was the best part of AOTD,
Silent hunter also had some great interviews!