I've had two Collings D1's in my possession for the last couple of weeks. About the guitars: D1 (Sitka/mahog dread), D'Addario p/b mediums, 1 11/16" at the nut, guitar is approx 1 yr old, I've had it for six months. D1A (Adirondack/mahog dread), D'Addario p/b mediums, 1 3/4" at the nut, guitar is approx 6 months old, I've had it for three weeks. About me: I play both fingerstyle (flesh & nail right hand), with a flatpick, and hybrid pick (pick between thumb and index finger, finger pick with middle and ring fingers). I have a light to medium touch, generally......only ocasionally will I really wail (usually just for single string leads, etc). So here's my short answer as to how these two guitars differ in sound. The Sitka guitar has a narrower frequency response, not quite as brilliant on the top end, not quite as large in the bass, compared to the Adi guitar. The Sitka guitar has a bit more midrange focus and punch, but the note separation when playing chords is greater on the Adi guitar. I vacillate on an hourly basis as to which guitar I prefer. So are the differences all due to the differences in top wood? I dunno. Probably, the Adi guitar needs more play time to "open up", so I imagine I will keep both for as long as I can afford to and make a decision down the road as to which to keep and which to let go. Or maybe I'll win the lottery and keep both!