Two points that I think are not subject to serious dispute:

1) The best (mechanically, and craftsmanship-wise) steel-string acoustic guitars ever built are being built right now, and in greater variety.

2) There is no way to build a new guitar and get the effect of "playing in" for 25+ years on the sound quality.

The ideal is to have an old Martin. But if you had one, you'd be scared to take it out of the house for fear of something happening to it.

The next best thing is to buy a new "vintage" line Martin, or a Collings or Santa Cruz, or a guitar from some private luthier, now, and wait 25 years.

Of course, I'm not talking about guitars for blues. Blues guitarists appear to prefer their guitars to sound as cheap as possible....

Peter.