There are several Morgan registry sets, and the answer to your question depends on which set you are talking about. For example, no extra value is given for PL/DMPL coins in the "basic" set or the "with varieties" set. However, in the "PL/DMPL" set and the "PL/DMPL with varieties" set, extra value is given. Most coins have a 1 point bonus for PL and a 2 point bonus for DMPL, but the tough coins have higher bonuses. For example, a 1921 has a 4 point bonus for DMPL. By the way, the PL/DMPL sets do not require that all coins be PL or DMPL (only 50% need be PL or DMPL). Finally, in the new variety sets (e.g. the top 100 set), no bonuses are given for PL or DMPL.
Yale is correct. For whatever silly reason only the 2 sets w/ "prooflike" in the titles are weighted. It is also worth mentioning that the Carson City set is not weighted (which makes absolutely no sense).
The weighting for individual dates can be found Here
Comments
I am not sure but I think you get 1 additional weighting point for a PL and 2 additional weighting points for a DMPL.
The weighting for individual dates can be found Here