It's faster, for one thing; trying to jam too much down MIDI can lead to logjams. Plus, as I noted, not everything goes over MIDI, but all of the synth's functions should be on the USB bus. The FH-1 also allows a lot of user-configuration, which will let you change the module's function for different purposes; you might want its internal sequencing on one track, clocked out of the DM12...or at another time, you might want to convert the DM12's signals into something with a lot of extra modulation and the FH-1's internal processor can enable that by adding the modulation per output. Or if you don't feel like using the DM12 with the modular but still need a controller for it, you can get an Arturia Keystep and that'll connect directly to the USB host port as well, without a need to route that thru the computer. Lots of options there...