[Arran]

On local stations you probably would not notice a substantial difference, though the 16X has a somewhat more powerful audio amp. But in terms of shortwave and long distance AM broadcast band there will be a noticeable difference, the 16X has a tuned RF amplifier stage, a second IF amplifier stage, variable IF bandwidth, and a larger spread in the shortwave bands, which means that it will be more sensitive, and selective. I'm surprised that they didn't throw a magic eye tube into this set, RCA seemed to like throwing those into cheap five tubers just to market them as six tube sets, this has ten, but then again they were probably trying to market it as being Hi-Fi since the focus seems to have been on the audio amp and not the front end.
Getting back to the pushbutton bank, I would not be concerned about the vinyl insulation melting off from tube heat, the rubber (or gutta percha) probably melted because they didn't vulcanize it properly, this set has more then enough ventilation above the chassis to prevent such things, unless the wire was sitting 1/2 inch above the power output tubes.
Regards
Arran