As you say, the interiors will be completely different, in layout and in scale and volume.
The S&S 38 is a classic, tumblehome design that Frank Butler had a big hand in when he was at S&S, before striking out to form Catalina on his own. As a boat of that era, it has the characteristic large "J", short "E" measurements that lead to large genoas and
spinnakers and high aspect mainsail.
They are pretty boats, and would likely sail well within behavior patterns of that era of design. Upwind work should be fine, downwind could be a handful at times.
The narrow stern and high counter make today's ever more popular stern mooring practices problematic, esp compared to today's fashionable open transoms, and getting into and out of the
dinghy is harder too.
This older design may well have better storage capability than the 380, as the new boats push their interiors out to the hull.
I'd expect a considerable price difference between these two choices.