I dont know how comparable these drivers are but if you had the choice what would you pick and why. What is the SQ like, how loud, how low all of those good things. It would be on 1000RMS.
IMO the DD2500s are the best all round sub from DD.They can take a beating,but effiecent.With the exception of DDs sq sub the 9100,I thknk the 2500s have the best sq.Both the new 25s and 35s have major improvements in all areas.I have only heard a hand full of Bl installs,not bad.The advantage the Bls would be SD.If u have the room to run an 18" woofer,If both are 15s or smaller I would choose the 2500s.
dont know much about the DD, but myself, my buddy, and a few others who have experience will agree, that 1000wrms is not nearly enough to get full potential out of the bl. the suspension is just to stiff, and doenst loosen up much after beating on it for a while.