Here is the difference between the stock speakers in a vintage twin reverb and JBLs. I am not sure what speakers are in the TRRI.
In layman's terms:
The stock speakers in a Twin were basically POS (Piece Of Shit) speakers. Probably Jensens at the time. People seemed to like them, because they "broke up nice". Stamped sheet metal frames, relatively small magnets, smallish voice coils. El Cheapo.
JBLs on the hand (D120s, K120s, E120s, and pretty much any JBL speaker) are simply the best speakers ever made. Rigid cast metal frames, massive magnets, patented flat wound aluminum voice coils, and high quality materials and construction. All this cost mucho moola, but worth it.