I looked into the Rubig and bought an Aixro. I think the Rubig is going to be very similar to a CR 500 in a TAG engine. It’s big and heavy with a low RPM range It’s probably got great low end grunt but lacks top end HP. I also think the overall production numbers are very low. I would be concerned about whether or not they will stay current or become obsolete.
The Aixro has a lot of power but the thing that makes the Aixro different is the way it delivers the power and the fact that it does it in a compact unit that isn’t very heavy. The Aixro drives like it has no power band. After the clutch engages you have torque regardless of the throttle position. It’s the polar opposite of a 2 stroke and better than a 4 stroke at giving the driver precise control of power output. It’s also much smoother than a piston engine.