After lurking here for several years and learning a lot from TZ members, I finally decided to join in.
A bit about myself. I have been interested in the Sub since I was a kid after seeing them in advertisements in National Geographic, Newsweek & Time magazines, as well as seeing Roger Moore wearing one in Live & Let Die.
I finally got the Sub Date in 1995, after working for 4 years. Then in 2003, I bought the SD. I like clean dial of the SD without the distortion from the cyclops. At that time, I considered it very thick but still comfortable to wear daily.
In early 2011, I got the Sub C. I consider the Sub C technically superior in terms of the adjustable clasp, solid bracelet, legible dial markers, anti-reflective cyclops, etc. My only gripe is the wide lugs which makes the maxi case looks square at certain lighting condition. I prefer the lug size of the GMT IIC which, IMO, flows better with the bracelet.
In Dec 2011, I got the DSSD, which i consider to be the ultimate dive watch (to me anyway). IMO, even the DSSD's lugs are more proportionate and doesn't have that "square case" look compared to the Sub C's. But the DSSD is too thick to be my daily watch. The old school SD & the Sub C gets the most wrist time.
I will try to post pictures next time, if someone is kind enough to post a link on how to do it.