DS has expanded research (ie get four points of laser research per tier and research for getting new craft like EWS)
DS has better capitals, they are worth easily 20 HCs (well not all but the Kol, Radiance, and Kortul are) but they dont really over balance the game
DS has bigger fleets (can sometimes cause problems with lag on weaker comps)
DS has many visual upgrades (Bailknight and Mansh00ters mods)
DS has more SC (EWS Bombers and Gunships)
DS has more epic battles
DS does not suffer from LRM spam (a couple of Caps can stop spam cold)
DS has better pirates (and if you want a challenge, put in MINIMOD Powerful Pirates!
)
DS has a larger selection of planets (from Ocean to Urban to Toxic)
more planetary bonuses (deadly secret is .......... interesting)