I have both opz and Digitakt. The way I would describe the main difference is that the digitakt is a drum machine with work arounds to do some of the things that the opz does.
The sequencer specifically is deeper on the digitakt, with multiple pages so each individual note is editable and p-lock able. This is my main gripe with the opz honestly, and in this regard the elektron style sequencer is much more powerful. In addition, instead of “step components,” the digitakt has pretty deep probability and organizational tools that the opz doesn’t have, although the opz can do some of these things through step components.
I literally was in your same boat. I love the opz, but the limitations on sampling memory and a few other things led me to explore the elektron world.
The main thing that you lose, that is crucial to how I make music, is polyphony. Although people will tell you “There is a work around for polyphony on the digitakt!” it involves a pricey cable and is tedious, as it records each note to a different track, and you have to resample to get the notes onto one track. Which works! But is seriously tedious comparatively.
I own both, and make music on both. People love the Digi boxes, but you give up directness for sure. I think if you had both the digitakt and Digitone, you can get an approximation of what the opz can do, but with much more depth. With the opz, I can create entire songs quickly and intuitively. With the digitakt, I can create patterns pretty quickly and easily, but, even with song mode added, I find it much more tedious overall.
Anyway, it is clearly a path you must follow, as it greatly depends on what type of music you make, etc. I find the digitakt much more suited to dance music, which is not really the genre that I work in, so that may be my issue with it.
I also own the model cycles, which is cool, and has its own thing going on completely. It is really great with other gear, and especially as a drum machine, but it is pretty limited as well.
Unfortunately, I haven’t really found another device that works as well for what I do as the opz. I just really wish there was a way to expand the sample memory so I could fill all of the instruments with samples, as I rarely use the built in synths outside of bass and arpeggiator. Hoping for the OPZ field, but also at that point, buying both of the Digi boxes may be more cost effective.
I know this is a lot of info, but elektron gear isn’t cheap! The upside is that the resale value is high, so you could always try it out and sell if it doesn’t work for you.