I have had a Huben K1 in .22 for a two years and love it. It is a fantastic, reliable gun. It is accurate, ergonomic, easily tunable, and very quiet once an LDC is added (it is not horrible without an LDC, but for comparison it is not as quiet as a Marauder at similar power levels).
I bought a .22 Sidewinder almost 2 months ago to "scratch the itch," and it is nowhere near as a good a gun as the Huben - the trigger is lacking, the gun is much louder than the Huben even at much lower power levels (and after modding it to wear a quality LDC), and the ergonomics, fit and build quality are not as good. A lot of the noise comes from the action itself, and a moderator does nothing for that noise.
That said, if I did not have the Huben I would probably absolutely love the Sidewinder. The Sidewinder is accurate, fun to shoot, and like the Huben easily tuned and adjusted for power - and the added full auto is fun on occasion.
I will say that the removable mag system on the Sidewinder basically solved a problem that was not a problem to begin with. It is nice to be able to swap a mag after 15 shots, but at ~$ 150 a magazine having spares is costly, and reloading them is actually a bit slower than reloading the Huben as they are a two part magazine. The biggest time element in reloading is picking up the pellet and orienting it to insert it into the magazine. It is nice to have the mag flat on the table to reload, but I have no issue reloading the Huben mag with it still in the gun (especially with the new aftermarket loading gates that are available - I don't know why Huben has not switched to one of these on their own).