The plot thickens. I actually had a 4th prediction: lower message rate. At the beginning, this seemed to be true (with quite some caveats). But at least since I raised top of the 22cm antenna to the same height as the 66cm one late yesterday, message rate has skyrocketed, surpassing the best rate I had observed with the larger antenna + old receiver at the same gain. (Message rate is generally lower when using AGC.) This breaks the 4th prediction. At this rate, the smaller antenna is going to surpass both planes spotted and positions, further breaking the 1st and 2nd predictions. So, in the end, the tiny wire antenna beats the large rod antenna in all measures unless the old receiver was severely damaged or defective.
Surely, the old receiver had received two or three impacts estimated at between 2g and 5g. (The last blow dislodged the USB connector.) But electronically, I cannot imagine these impacts having an effect on any of surface mounted components or the PCB. (I did measure DC voltage after USB connector. There was no difference.)