DSSD really has no dome, maybe a 1mm. I had one and didnt like it. It was too top heavy and bulky, I have a 6.5" wrist. If you have a larger wrist it might work for you. It doesnt work too well under the shirt sleeve. I loved the glidelock but once again my wrists are too small, it just didnt sit well on MY wrist. I have a Slevin, cousin to the Cousteau. I love it. 42mm is perfect on my wrist and very functional. The internal bezel is a pain to move but it adds to the look of the watch. Both are durable. I worked retail and both held up very well.
Stuff to think about....
Decide if you want a Diver or Chronograph
The DSSD is the hot watch at the moment. If you are trendy go for that. if you like to be different go IWC.
Do you care about "pulling a watch off" if you do go for the IWC.
The IWC looks good on a bracelet and a rubber strap, gives you a little variety.
The IWC is a lot more functional: Bezel, chrono, day, date.
The chronograph movt wont last too long and really should be serviced as soon as possible to increase the longevity of the watch. Expect $225 to cover that.
Good luck with your decision. Keep us posted and post pics of your purchase.