Yay.
My A4 is currently boxed up, waiting for USPS to open so I can send it on to it’s new home with a fellow Elektronaut. I picked up an Analog Keys on Saturday morning and had them side by side over the weekend before I reluctantly boxed up the A4.
I didn’t really push the bass, but I have a fair amount of bass in some of my patches. With the same pair of Sony 7506s on I think the difference in sound between the two devices is small enough to be accounted for by random component variation and aging in different environments (the A4 spent most of it’s life in humid Seattle, the AK in the dry SF Bay Area). If this is a serious concern for you then audition all three devices before you buy. But for most people I suspect the sonic difference will be negligible.
I bought my A4 originally to sequence my Eurorack. But I ended up using it as a standalone bassline / monosynth instead. It doesn’t try to be a 303, but it can produce very nice acid.
I haven’t played with an A4 Mk2, but I did trade my Mk1 Octatrack for the Mk2. The Mk1 OT was too awkward to use, and the Mk2 UI was a huge improvement. The A4 UI is fine as it is. The AK UI is a little better, but I bought it for the keys & joystick. I’m sure the Mk2 is nicer than the Mk1, but I found the Mk1 pleasant and easy to use.