OK. Here's the comparison
Construction
First impressions in the hand are good. The RS1s must weigh twice that of the SR80s.
The headband on the RS1s is lightly padded, made of stitched leather and is wider than the SR80s, which lacks padding and is made of platic. The plastic junctions between the headband and the phones themselves is the same on both models. However, the metal bar used to attach the phones to these junctions is more substantial on the RS1s and square in section The SR80s are round and tend to swivel around more.
SR80 on left.
The metal "spring" in the headband is different too; on the RS1s it is stronger but doesn't exert as much pressure on the ears as the SR80s making the RS1s more comfortable to wear. Note: the earpads are further apart on the RS1s when in the relaxed position (see below).
SR80s on left
The remainder of the SR80s are constructed from plastic. The RS1 use metal and wood. The ear chamber of the RS1s is bigger (at least twice the size) although both models use the same foam ear pads.
SR80s on left
The cable on the RS1s is slightly thinner than on the SR80s. Both are flexible and feel "nice". The SR80s are terminated with a mini jack and come with 1/4 inch convertor while the RS1s are terminated with a 1/4 phone plug and comes with a substantial mini jack adapter.
SR80s top
The RS1s are a more refined product with all aspects of the construction superior to the SR80s.