Point taken, but as I understand it? During the period the OP has specified the 30mm M-shell was very much a "new kid on the block", whereas the 20mm variant was in widespread service. If I'm understanding it correctly (and please "straighten me out" me if I'm off base here), the /U4 mod for the 109G-6 was only just entering service and Bf 110G-2/U9's were (likewise), only starting to reach frontline units for operational testing (ZG76) in the Autumn of 1943?
Fully agreed on the "horror show" factor of one vs. the other. The 2cm was bad enough...the 3cm round was absolutely brutal.
Nothing succeeds like excess.