DM is a MIOS based hack, and as such, runs in GC mode. Devolution runs in Wii mode. They may achieve similar purposes (to an extent), but they are very, very different programs. DM can't be "improved" to a point where it is level with Devolution; it's just completely different. DM can't have some features existing in (or planned for) Devolution. For example, I don't believe audio streaming can be implemented in DM, because of a lack of resources. There are also reports of some games having smoother frame rates etc. in Devolution, due to them being run with additional processing power. In addition, it's possible (and indeed has been demonstrated on video) that Devolution could work on the WiiU; DM is quite unlikely to work there I believe.
Of course, for warez kiddies who just want to play their pirated GC games, DM does the job fine. But for the best GC experience possible on the Wii, it's always going to be Devolution (and I include official GC compatibility in that).