I too think the early SupeRadios were the better ones by far. Built stronger with air variable tuning capacitors in the first version I believe. A 40 year old Super can still play if taken care of, where many are having problems with jumpy tuning on Super 3s, due to the tuning voltage carrying DC and polarizing the contacts, especially when the radio sits for a while.
Going by sites about this, they used less proven and reliable technology, but the reception, if the SR3 is tuned up well, is supposed to be superior than earlier Supers.