There is enough history /past threads etc here to fully cover the attributes and draw backs of various powders. Mad Monk has a complete article on this subject . Some of the "subs" are corrosive, some are erratic in terms of power [ higher pressures than you may desire ] , some draw moisture more readily than BP , some have less power , so lower velocities,
many don't have the long term storage capability of BP. All have higher ignition temps than BP
Having shot in long range matches [ 1000 yards ] I believe that only BP has the accuracy potential to compete. Subs don't do it. Even duplex loads [ smokeless + BP ] can't compete with BP . So, basically, the only reason that you might want to use a sub is their availability [ dealers find them easier to stock ] , however, this is a rather thin excuse if you really want the best results from your long rifle.