about 6 months ago I did an extensive, in-store search, for a good-sounding 12 string for gigging. There was absolutely no brand-influence at all. But sound-wise that Martin fell out of the running before I hardly got started. I played one chord and handed it back. To shorten this post, it came down to a Martin D12-28 or a Taylor GS-5. I spent nearly two days playing 12's and a total of several hours between those two trying to decide. Frankly, I preferred whichever one I was playing. What made the final choice for me was when the sales rep played both so I could hear them as a LISTENER, rather than a player. I found the Taylor to have a tiny edge to my ear. It seemed to have a slightly better sound balance than the 12-28.
I have owned/played 12s for many years and have owned (not in this order): Seagulls (best sound for the money) Guilds (worst sound for the money), Ovations (blah all the way around), an old FG Yamaha (my first 12 - sounded great but finally ended up needing a neck reset and it wasn't worth it to me at the time.
IMO, the Martin 12 you are considering will be a disappointment. If you have no 12 string experience I REALLY recommend you go play some of them before spending any money. OTOH, if you have no 12 string experience, I suppose any of them will be "different" enough to be interesting, at least for a while.
