Sherwood is one the oldest if not the oldest reg manufaturer around and I have noticed when working on some of the older Sherwood regs that they breathe very good - far better than they have any right to breathe given the otherwise average downstream unbalanced design. I suspect they were just well made and squeezed every bit of potential out of the design.
Regulator performance has not significnatly improved over the last 25-30 years. Most "new" developments have centered around plastic cases and similar changes in materials to cut production costs and unfortunately this has often meant a slight decrease in performance. And the European Norm free flow resistance requirement that serves mostly to detune second stages has further added insult to injury.
So in essence much of the "vintage" appeal in some regs is that the regs of the era were of much higher quality and were designed to last a diver for his or her entire career. No cheap plastic and no designed obsolesence.
If manufacturers build the quality back into vintage designs I suspect they will sell very well and that people would in fact probably pay a bit more for them.
