Bob, I largely agree. Where it comes to the weight differences, I'd said "it depends." If someone buys a Kubota B and fills the tires, the comparison to the CK20, unfilled, doesn't yield a spit's worth of difference. If the Kioti owner opts to fill his, of course, it might yield a slightly better dirt working machine, all things being equal. But to that last point, they never are - differences in hydraulics, buckets and edges, and other specs, even parts fit and finish - conspire to make every machine (or design, anyway) different.
As you said, the Kioti is a CUT. The constant attempts to make it into "a class of its own" strikes me as a real stretch, and my-brand-vs-yours nonsense. We're not talking about differences like a CUT vs a dedicated TLB (think the
B21) of the same HP, for example, or comparing a CUT to a Power Trac or a skid steer. THOSE are class differences. We're talking about spec differences - and for that matter, one material spec difference.
I won't comment in detail on the frame vs integral construction, as the subject has been hammered to death elsewhere. Suffice it to say that the Kioti, again, isn't alone in its construction among CUTs.
As far as classification, whether based on size (and I'd include weight), operational specs, drivetrain, configuration (e.g., front engine, MFWD or 2WD, 3PH, PTOs), intended use, HP, tires, targeted consumer group, or any of the common distinctions, the CK sits quite comfortably and normally in the CUT class. To maintain otherwise is to lose all perspective of tractor classes. Think of them and how they differ: row-crop tractors, orchard tractors, TLBs (dedicated, that is), tricycle, tree-farm and nursery narrows, double-enders, articulated, etc. And yes, UTs, CUTs, and sub-CUTs.
None of this is to say that one can't make an argument for Kioti, or any brand or model, for that matter, being in a class of its own based on some subjective criteria (like quality). I think that's a tall order too, though. I have a hard time seeing how any among the so-called major brands stand head and shoulders above the others, never mind Kioti.