I have had a Martin Slimline in my guitar for ever - running through a Passac preamp, which is tuned to the body resonance of the guitar. The net effect of this is to produce a very natural sound for a bridge pickup, with very few problems with feedback. A number of sound technicians have told me it is the best sounding pickup they have ever heard in a guitar.

However, no pickup sounds the same as the acoustic sound you get sitting in front of the guitar. You can only capture that with a good instrument mike. You need something with a flat response down to the bass resonance of the instrument, plus a clean flat midrange and top end. I have used a Beyer M800 for recording, and it is good.

Voice mikes are a good choice for live performances, because they have fewer feedback problems than instrument mikes. However, all mikes have feedback problems on stage. Sound reflects off the front of the instrument, causing high frequency peaks, and the resonance of the body is amplified.

The Beyer is OK for stage performances, but it has good bass response, and this can be a major disadvantage in the feedback department. Cnsequently, I always rely on the Slimline.

Regards
Chris