You can probably get a used pair of Shure SM81s for cheaper than a matched pair of MK-012s. I have three SM81s (one of them "modded") and one MK-012 (also modded a little), so I can only do stereo recording with the SM81s.
Which one I like depends on the guitar. My main acoustic is a 1972 Martin D-28, which has a full sound - I like the SM81(s) best on it. I have a couple of others with a thinner sound, and I like the MK-012 better usually for those (wish I had a pair). The SM81 is too honest

-- the Mk-012 is too much on the Martin.
But while we're on the subject of the Group Buy, sign up for two ACM-310s! They might not (probably won't?) match in the stereo sense, but they're inexpensive and sound good.
Never used NT5s, so I prolly shouldn't vote. I have
a MXL 991, which is like a 603. I didn't like it (edgy, smeary, phasey), so I went nuts with a soldering iron - it sounded better after changing the main coupling capacitor, but it's still a little bright, and I don't use it. BTW, Marik reported that the ACM-310 uses essentially the same capsule as the 603, but my 310 sounded *much* better out of the box than the 991 (maybe it's the tube, and the overall design, etc.).