from experience, my vote will always be for speed & responsiveness (in all of these: button action, reeds, & bellows) over "authentic" voice, every time. i love "authentic" concertina reeds, but the accordion-reeded sound has its own loveliness, and the advantages to the development of one's playing---yes, speed, but not just speed---phrasing, ease of ornamentation, expression, etc---of a fast, easy, responsive accordion-reeded concertina versus a more labored, huffy-wuffy concertina-reeded instrument, would be no contest. of course, not all "hybrids" are optimally fast & responsive, that's the rub......
I agree that a good new box with accordion reeds will be better than a middling old box with funky concertina reeds. I doubt you could get an old Anglo for $3,000 that would be better than a modern Kensington, made by Dana Johnson. His concertinas have true concertina reeds, firm and quick action, great design, and beautiful construction. The problem is they are hard to get, with a lengthening wait list.
Have Tedrow, Edgley, et. al., considered making a box with real concertina reeds?
Such an instrument would certainly be attractive to players.
Does anybody sell sets of concertina reeds?
Would the increase in price not justify exploring that possibility?