yo, the feature list speaks for itself - to me, that's more than adequate reason for why i think someone should switch, and enough has been said and done about the features.
but i'll address this part in full:
i am a fan of doing things live as in not having to press stop unless i have to...
in order to most fully use any editing software no matter where it's found, you're truly gonna have to break this habit unless you're going to record everything from the main screen exclusively. this type of workflow is good if you don't want to edit, like...at all, but starting/stopping/rewinding/starting/listening/stopping is a rapid-fire process that is integral to deep editing to get your complex tracks sounding exactly the way you want them.
the other option is to build a track 1 pad at a time, relying on your timing to correct your mistakes and waiting for the sequencer to come back around before making your change. if it's just a matter of playing/recording pads over a live sequencer, an sp303 is adequate, wouldn't you say?
this isn't to say you can't get quick with your fingers. get good at playing pads, and there will be less deep editing. however, starting/stopping rapidly is something that i've found pretty integral to the mpc in general, even when i was programming everything in step edit. if i didn't want to edit, i'd be working with an sp or better yet Reaper and vsts exclusively. the main strength of os2 and os1 for that matter is its fast, intuitive, painless editing process, most notably Midi Grid Edit.
the piano roll in jjos is the single most comfortable, pleasurable sequencing interface i've encountered in my short life.
i'm sure this response wasn't exactly what you were looking for, but hopefully it does you some good
