Although I'm probably closer to being the producer with a studio full of gear than a live performer or player, I still struggle with anything other than full-size keys. The only mini-keyed thing I have is the MS-20mini and I treat like a module. The keys themselves are literally gathering dust. The rest of the synths here are for playing, however incompetently, and sketching out ideas. I can do that on full-size keys without looking.
A parallel to this is scale lengths on different guitars. My main guitar, a Jazzmaster, is a full 25.5in scale length. One of my other guitars is a Jaguar, which has a slightly shorter scale length of 24in. I find it almost impossible to switch between them without fumbling chords, and the difference there is much less than the difference between full-size and mini-keys.
Personally, I would hesitate before buying another mini-keyed instrument. Instruments are such tactile things and I don't feel the same connection to a synth I don't want to physically play. I struggle with modules and soft synths for the same reason.
It's just practice though I guess, guitar scale length has absolutely no impact for me but I regularly play lots of guitars with different scale length and profiles, also 1/2, 3/4, baritone, banjo, longer scale bass etc. So I guess I have no standard.
It is more difficult when they are fretless, this can take a while to get your finger placement in tune but I guess this is just practice as well in the end.
What I do notice is that scale length can make me prefer different keys while noodling along, probably to do with general comfort of arm placement.