My KH20 double crown arrived today. I have only ridden my KH24 before and hopping on the smaller uni was quite a surprise.
They really are different machines. The 20 feels much lower to the ground and raw, the 24 feels tall and luxurious by comparison. I bought the 20 to help me acquire trials skills I can translate into riding muni on the 24. First impressions are good. The 20 is much easier to hop on - I hopped around 360 almost at the first attempt - and a brief try at idling was very encouraging.