I bought a pair of Dominux8s for a general-purpose multi-game MAME cabinet but I definitely was interested in suitability for Robotron, specifically.
I'm a 750k Robotron player on my best day so not really an authority of any kind on that game, but there have been a few times I have spent time playing original Wicos on a real cabinet, followed by coming home and immediately trying my setup, to get a bit of an A/B comparison on the joysticks. The most conspicuous difference in these trials, for me, was that the original sticks seemed to have a noticeably shorter throw before they hit a stop. The originals also might have a bit more firmness in the centering spring, but then again, I've played other cabinets where they were really loosey-goosey, so it probably depends on the condition/age of the grommet.
For what it's worth, my D8's have been pretty solid and consistent for 4-5 years now. You definitely have to spend some time to tweak the leaf switches to your liking but once I did that, it's been largely set-it-and-forget-it.
Regarding original Wico vs. Dominux 8, personally, I'd not call either stick "better;" they're just a bit different, and you're likely to find some players who prefer one, and some players who prefer the other, just like anything else. Of course, it goes without saying that if purism is important you can't beat original hardware. But if, like me, you want an excellent leaf switch stick with buttery smooth circular restriction that plays a great game of Robotron but also does well on hundreds of other games on a general-purpose cabinet, you can't go wrong with the D8's, IMO.