The A|4|Rmk1 design (and form factor) is great.
You could go with the mk1, they are so cheap on the second hand market it’s criminal.
Now, sequencer wise, the A4 got it all (and more with trig mute, slide, accent…). The arp can be random but the Digitone arp can’t…
Let’s say you’re a guitarist and I tell you, you can get chorus, delay, reverb (with infinite mode), filter (=wah) and a sequencer to program the FX changes for your songs, you would not be surprised at a $500 asking price.
Let’s say you’re a modular guy and I tell you, you can get a sequencer with 4 VCs freely assignable with arp, p-locking, LFOs for $500… that would seem cheap. On top of that, you also get FXs and an FX sequencer and filters… even cheaper.
and now, you have an analog synth engine on top of that and a pretty deep one at that…
Now, the A4 raw sound is not exactly the most enticing compared to say my Rev2 or even a simple Minitaur but… it’s a crazy good drum machine, great for FX patches and pads, bass and everything in between. It needs work though. Well, you can use patches made by very good sound designers, nothing wrong with that! my Rev2, Minitaur, Digitone can’t sound like the A4, the A4 has its own color and only you can tell if you like it or not.
I’ll never sell mine that I can tell you!