I guess if you wanted to expand your list, there are some emulations of classic drum machines out there that could qualify as competition. (If it were for me, I would take another look at the TR-8, for example--but your mileage may vary.)
The Digitakt is a problem-solver and could pair well with a MicroKorg, but if I were thinking live with that set-up, I would have to decide, for sure, if I could live without velocity-sensitive pads. I think the Digitakt's the most powerful and can fit into a lot of setups in ingenuous ways, but (and this is also just to me), I would feel like I was committing to planning a lot out in advance, since actually playing drums with it would be, well, more like a drum computer and a little less like a drum machine. Then again, if I wanted to sample live as part of the performance, Digitakt would probably remain on top. For studio, it's what I'd want most and I loved using the DT. To me, the speed and design blew the others away, though I don't know the MicroBrute well.
For me, I haven't found Drumbrute demos online that have made it sound like it's for me. I like aggressive and stompy stuff, and I'm just guessing, but I think I'd want to run it through pedals. So, to me, it would be different--but if I liked the sounds, like got to try one and was wowed by it (which you seem to be describing), then it would definitely be near the top of the list for live use.
And the Electribe, to me, is a lot more powerful and "usable" than the Volca Beats, where I've used both a little and they're fun and certainly worth considering. If the Electribe workflow speaks to you, it's going to be able to cover a much wider range than the DrumBrute. So as a creative tool for exploring, the Electribe is closer to the Digitakt, though I feel like the DT is much more powerful in ways that make sense to me--but the Electribe is velocity-sensitive and, like you mention, it has a card that's a little easier to deal with and can play nicely with Ableton. But if all I wanted was a beat and the MicroKorg would be the star, and money was tight? The Volca Beats would win because it's priced right and can handle some stuff relatively well.
So those are my thoughts and I agree with the idea that going over the specs and your likely uses will help balance out how the DrumBrute is the most drum-machine-oriented, like a more traditional tool based on the legacy of drum machines; the Digitakt is (to me) extremely fast and a joy to use in a way that blows my mind, and can do a whole lot of different things--but plenty of those might not apply to any given use; the Electribe 2 is well-thought out and interesting, with the compatibility and velocity strengths; and the Beats is significantly more affordable and the size makes it a lot easier to carry around. None of them seem like really bad ideas to me (taking into account the Volca price), based on what it sounds like you're thinking.