The BK5 gives you increased ability to edit styles, and to create your own "user" styles. The BK-7m has a couple more options for connecting to a MIDI accordion or MIDI guitar. Neither one has a fully-featured on-board sequencer. (Beginning with this generation of product, I believe Roland expects you to use a PC-based software sequencer like Sonar LE.) However on the Roland Arranger forum, Diki expressed doubts about the reliability of transmitting dense arrangements to a PC via MIDI USB. If you really want an on-board sequencer, you might consider a Prelude or GW-8, which are still readily available and otherwise very similar. All of these options are about the same street price. My $.02.