There is no reason the Retro guitars should not sound like standard Martins unplugged, they are standard Martins!
All the Martin/Fishman acoustic/electrics (less a couple really high end Madi models), first generation and Performing Artist, are mortise/tenon necks with hybird X or A frame bracing, they are physically different than standard Martins and they sound different. I have the top line of the Performing Artist series and I seriously don't touch it unplugged. It's purpose in life is to be amplified and the voicing is for that usage. Unplugged IMO "not so much", but that is against some pretty high end models to be fair.
The appeal of the Retro series is you do have a traditional Martin that will sound great unplugged, but you then have the latest/greatest electronics for band/stage work.
You don't buy an expensive nail gun for just one handiman job, don't buy an acoustic/electric if you plug in twice a year or don't perform............
