I had an analog four and now have an AK.
The scroll wheel makes a big difference, as browsing sounds and using it for various other functions makes some tasks easier.
The joystick is hit or miss imo. The fact that you can’t record it into the sequencer makes it useless for most of what I do. I’m guessing it will be more useful to guys who play live than anything.
Sequencing patterns is much faster with the keyboard built in, and the multiple outs are a life-saver when I want to use it with outboard or to mix down. Also, the visual feedback on what notes are on what step is helpful.
I don’t think it’s worth it to switch from an A4 to AK… the overbridge should compensate for the lack of outs on the A4, and you can always just use a midi controller if you need a keyboard. The jogwheel isn’t a game changer.