A4 works better for modular gear and analog synths due to CV in/out. I love using mine with Make Noise 0-coast to sequence the synth while adding drums and pads for a complete package. The AR is great if you want a serious drum synth. BTW, has Elektron fixed the freeze bugs with the MK2 version of the AR? I have two Elektrons: A4 MK2 and OT MK2 and love them but held off on the AR due to the freeze bugs that plagued the machine for a while.