Mark, about half of my Astro League double stars so far have been with the 4". And yes, it was only the DTP that guided my choice the other night, since I had put it back on the Celestron. Aperture is wasted on double stars. Oops, did that come out of my mouth???
In fact, Greg S and I have had some discussion about our 15" dobs not being the best for splitting some stars, especially bright stars with dim companions. Seems the fast dobs are prone to 'blooming' the bright star and overwhelming the dimmer secondary. Certainly, he and I have both come to the conclusion that the double-double is best split by a refractor of almost any size versus a fast dob.