I was also an SHIII Player before i started DW. SHIII has much better graphics but i get bored. Because always the same kind of Action and the poor WWII Technology.
Then i downloaded the DW Demo. My first opinion was "Wow thats what i have searched for" But after a few minutes "omfg, that game is hard to learn".
But then i found an German Tutorial how is really really great and helps me to handle more and more stations
http://www.space-port.de/dw/index.html (if u are German
So my opinion is if u are ready for an complex game that needs a lot of learning then play DW. (try the Demo first then u see )