What are the years? ;-)
To the point: the OM28V.
I guess another way of answering would be to suggest you send them all to me so I can play them for a few months. Only then will I be able to tell you which one I like the best.
OK, so you meant which model of the ones you currently own do I favor - as opposed to the exact individual guitar. This is quite a list - you have an impressive collection! I do favor the OM body, though a close second is the 000. I have an Eric Clapton model (28) and really love the way she plays and sounds. Without looking it up, I believe my EC model is an OM-28V but with a facsimile of Eric's signature. But I hear differences in various guitars of the same model. Some of the differences have to do with age, I'm sure, but I believe they each sound unique because of small manufacturing differences. A lot of folks criticize Martins. These folks are usually of two types: Those who want a Martin but don't want to afford one so they focus on Martin wanna-bes and those who can afford to hire a luthier to build a custom instrument.
My opinion (as if anyone cares) is that Martin has done the best job of producing a factory guitar that emulates a one-at-a-time custom guitar. Some say it's their marketing that did it for them. It's true that mythology is a wonderful thing for a salesman since it supplants reality with romance and substitutes lore for fact. Armies of Maidson Avenue advertising executives work tirelessly to crate just the right mythology for their clients' products, sometimes succeeding amazingly well (BMW) and sometimes failing dismally (New Coke). As the Canon Camera advertising used to say: Image is everything.
However, Martins deserve their niche in the guitar world as the best factory guitar you can buy and their sound created their image. I believe Gibson comes close, but is not as consistent as Martin has been (and I love Gibsons). Martin would not have survived for so long, nor would they be THE choice for bluegrass (HD-28, D-28, HD-28V) had they not been simply a great guitar. Ever notice how others, when criticizing Martins, almost always compare their guitar to a Martin? There's a reason for that.
So what you have there is a very, very nice sampling of Martin's dedication to producing a well built, great sounding guitar. Looks like you prefer the smaller body sizes. Me too. The OM model I chose has the size I like but also has fantastic balance across all strings and frets. I like the string spacing for fingerpicking on my EC model; I suspect your OM has the same. Martin's vintage series breathes new life into the benchmark characteristics of their success.
Backpacker (steel string)
I'm very partial to OM-21s. I've always thought them to have great balance and value. However, I like best those with a rosewood fretboard and bridge. They strike me as having a somewhat more "woody" tone. Is your fretboard and bridge rosewood or ebony?
I go with the OM-28V as a veristile guitar with a great sound, neck, body size and bracing.
You have a nice representation of Martin guitars.
A 000-28(or 42)VS would bring some 12-fret representation and the ear-catching tone they offer.
Martin 0-45S Stills
Martin 000-42 Koa 12-fret
My edit did not work...my 000-42Koa 12-fret is the nicest (to me) sounding guitar outside of two others I have played (but not owned): a 1934 00-40H and a 1932 OM-28. Twelve-fret guitars have a voice which just says "Listen here!".
The 000-16ST is one of the best all around guitars you will find. A very versatile guitar and a very practical price tag. My Favorite Guitar has some with bone nut and saddle.
I have always been partial to 1973 D-28 # 336474 it's the "one" I like the best.
I have had numerous Martins. The D-28S with the slotted head and 12 clear frets is an awesome guitar. Peter Yarrow of Peter, Paul, & Mary played one on the early albums.
In 1972 I bought a Framus, and still have it, but I always wanted a Martin. For two years I stopped by Guitar Center every week or so and eventually played every guitar they had hanging in the room, both Taylor's and Martins. I fell in love with a Martin PA3 and never switched again as the sound was just fantastic to my ear. For months I stopped by to visit my "baby" and play a few tunes until I finally boke down and bought it. I'm not sure why I bought this one because I rarely play in front of people...I just love the tone and it makes me sound better. I guess I agree with the the earlier comments. It's not necessarily the model but when you find the one that makes you stop and go "wow" then that's the right guitar.