If you want complexity in ship design then I can't really recommend DW as it's ship design is limited to adding components with weight and energy requirements to certain hull classes (escort, frigate, etc).
However, in most aspects it is the best 4X game I've played. The civilian trade network and vast potential scale sell it for me. The game doesn't really have any unique features (in regards to gameplay and mechanics). What it does have is basically all the various 4X mechanics combined in a single real-time 4X game.
I will however warn you that most people seem to regard DW's learning curve as quite steep. I never found it so, but I enjoy learning the way a game plays and am willing to restart many times in the early days. I also went to uncommon route and switched off all automation from the get go (another cool feature - the whole game can be automated and you can sit back and watch how the AI deals with your empire).
My biggest complaints would be;
- The lack of graphs.
- The lack of decent fleet management.
- The inability to customise species.
- The lack of differing types of ftl.
Looking back at how much I've typed I come to the conclusion I must really like DW.