For me the biggest factor in the S37 over the A4 was that i am unfortunately very ‘time-poor’ … only get about an hour to play music every day. The S37 is so immediate, sexy (i call her ‘scarlett’:), tweakable and fun … the A4 kinda lacked that immediate fun factor for me, felt more like a cold, sound design tool which is cool but again no time!! (and yes, those tiny screen and knobs!) … For me, the elektron approach / sequencer works better for drum machines (i have MD and AR) … If the AK had come out before I got the A4, I may have got the AK, but IMO it still appears a bit cold / too much menu diving.
Anyhow, here is a quick vid of the MD thru the S37 filter … TBH, I think it sounds pretty rubbish (the MD/AR filters sound much better) and would never use it, but may give v00d00ppl some idea of the sound …