Agree with everyone also the good thing about a hopper - even if you plan to DL on a certain day you may get there an it be insane where as DCA could be less crowded. Gives you more flexibility. Right now I don't feel like DCA is a full day park - it's more like a 1/2 day if you have maxpass.
Even if you don't hop for the rides, you might enjoy it for the food and/or grown up beverages. Alcohol is served in DCA, but not DL (unless you are a guest at Club 33). In general, we like the food better at DCA and will hop over there to eat, then hop back to DL for rides and shows. As others have said, hopping is so easy at DLR -- DL and DCA are really more like one big park.