I think you're experienced enough by now to know if you should try different gearing or not for the routes you ride.
As for weight, I'd go for the lighter cassette since you've mentioned you wished you'd bought lighter components. Lots of the Ultegra vs DA weight savings is in the crank and cassette.
Be warned, the 2011 style 1 piece cnc SRAM cassettes are loud (I have an "old" 2011 style 1 piece steel SRAM XX cassette and it's super noisy). DuraAce also seems noisier than ultegra but not as bad as the XX cassette. The new RED cassette for 2012-2013 is supposed to be light *and* quiet, might be worth a try if you have money to experiment with.