I personally own an SF-12 and the studio where I work owns a pair of Coles 4038s. I do like both mics, but here are my observations:
- The Coles 4038s are more versatile and generally sound good on most instruments, especially when it comes to sax and piano. Used it on guitar too with great results. Being able to arrange them in Blumlein, spaced pairs, or individual mics is a plus as well.
- The SF12 is a beautiful, very natural-responding mic. I usually find myself adding high end... and, if I remember correctly, there is a bit of a "honk" around 800Hz that I usually reduce.
- Pres I've used with both of these mics... Millenias, GMLs, and APIs. Great River, too, though not recently.
- My two favorite piano recordings were done with each of these mics. One was a jazz recording in-studio... lid off, Coles 4038s directly above the piano, spaced above the high and low strings. The other was a pop-classical performance in a large church with the SF-12, lid at full stick, mic back a few feet from the crook of the piano.
- I like SF12 on trumpet, have not liked it on alto sax. Also have not liked it as drum OHs, but I'm a Heine U87 -> API pres kinda guy now. I have not tried the Coles 4038 as OHs recently (they are always on a horn).
- THE ROOM IS KEY, especially with the SF-12. If you plain to use the Blumlein configuration with the SF-12, you NEED A GREAT ROOM. Lately I have leaned towards recording every instrument in Blumlein or ORTF... as far as isolation goes (and I record jazz groups in with the musicians standing in a circle in the main room, drums in a large booth), I've found I can "set it and forget it" with the Coles 4038s, but the SF-12 sometimes requires some adjustment. However, the SF-12 is easier to position!
They are both great mics... I am hesitant to give you a solid recommendation either way, but I will say the Coles 4038s have gotten more mileage with me. If you go with the Coles, BUY TWO. Stereo is king - you have two ears, record with two mics. If you go with the SF-12... enjoy! And take care of both