I own both, though I’m not a power user of either yet.
From my perspective, having the pads on Hapax makes it a lot more immediate than the Cirklon. Operating the Cirklon isn’t bad or anything, it’s more that you don’t get the note input on the unit aside from using the encoders. There’s only a note preview function on the P3 type tracks, by holding the step encoder then pressing the key below. Putting notes in is mainly done using the encoders above the steps, which works, but feels a tad less quick in my experience. That or playing in the notes in real-time, or step-time, or if you’re using a CK pattern, by tapping the sculpt key (also in real time and for the selected note row).
There also is no full equivalent to the Hapax piano-roll-style input in the Cirklon, as you only get that style of visual feedback in CK patterns, and mostly on the display as the step keys only show one row/note at a time. How big of a downside for the Cirklon that is would probably vary between users, but I think the Hapax is a step above here. Note selection using the pads, and the visual feedback, and so on…
I could go on and list more detailed comparisons (and I will if you ask, of course without trying to derail this thread), but I think the most succinct way I can put it is this:
Cirklon feels very deliberate in its approach, to a greater extent than Hapax at least. Hapax, in turn, feels more exploratory to me, with a lot of more immediate tools for ‘spicing up’ a sequence, exploring alternate arrangements of patterns and so on. This is reflected in its built in probability and math parameters, the MIDI FX, the interface itself, and so on.
Example: in the Cirklon, switching patterns on a given track requires you to select a track, go to the track page and then select another pattern from a list, for any single given track. In Hapax, the most immediate equivalent action only requires you to hold the patterns button and tap a different pattern on any track. Or several at once.
To summarize - the Cirklon to me feels more like something I’d compose a piece of music on that I have a good idea of where I want to take, and the Hapax would be my go to when I want to mess around and find my way forward as I go. 