as stated in post#2, room acoustics are a important factor, and the better the mic, the more you´ll notice that.
that´s less important with a ribbon mic like the m160, but you need very good preamps with ribbons (low output)
i also recommend trying to make a stereo recording with the AT4041 AND the Neumann (or whatever mics you want to try).
Acoustic Guitars are so much nicer in Stereo. Don´t go for a "perfect" stereo setup, just point them to where it sounds good.