When comparing similar microphones for a given task, like the acoustic guitar recording demonstrated here, I think it's important to use the same performance, recorded simultaneously, with carefully matched levels. Without these precautions we're not really comparing the mics fairly.

This first video demonstrates setting up the microphones and calibrating the mic preamplifier gain.

Part 2 demonstrates a recording session, followed by a final round of gain adjustment, to create the matched clips for comparison.

These videos are part of a blog post on the Homebrewed Music Blog, homebrewedmusic.com where you can find links to the sample clips created in these videos and to the software tools used.