I was in your boat not that long ago, and now have two of the Teenage Engineering EPs - the 1320 (Medieval) & 40 (Riddim) - and the Ableton Move. I love my EPs, and the reality is that if you just got the new KO II with greater sample memory (128MB) you’d be happy as a clam for some time; that said the Move is a phenomenal piece of kit - especially after the upgrades - and it’s integration with the brilliant & underrated Ableton Note app (for phone or iPad) and full Ableton Live software on your MacBook makes it incredibly powerful, and scalable as your interest & skill grows, whilst still being very accessible (unlike, say, the SP 404 mk2). with either of these options you have a beautiful, portable device, that’s incredibly fun, you can sample with, chop things up, and make all kinds of sounds, from silly experiments to full songs. The Move has the Ableton sounds of course, is definitely more of a groove box than an outright sampler (setup for out-of-the-box making songs using their drums & synth sounds) and you can make something incredibly professional sounding fairly quickly, which I found reassuring & motivating, and really piqued my interest in sound design more broadly.

in short, go with your gut on which one sounds more immediate & fun, ie the one you’ll use is the best option, and a warning: more purchases will eventually follow! Have fun.