A friend of my purchased the 380s pre-amp and I at the time owned the REF 3. I can tell you that both are excellent. Quite open and detailed. I don't know about the 38s but, I imagine that it would be close to the 380s with the 380s probably being better than the 38s.
However, I also compared the REF 3 (with new tubes) with a REF 5SE and I have to tell you they were very close. It definitely was not a jaw dropping difference between the two, and my REF 6 is not far away from the REF 5SE. I had all three in my house at the same time to compare. That was fun.
The REF 3 with new tubes is very hard to beat and for the money, impossible to beat.
Don't get me wrong, the 380s was excellent and I would take either one. if the 380s is an upgrade to the 38s, then the REF 3 would definitely be better than the 38s.
enjoy