Mic arrived on schedule Friday.,
Fairly large box, with the mic in a sealed plastic wrap (good thing, it was cold, so I left it sealed up until today), a zippered pouch for the mic, plus a foam windscreen in a box, and a shockmount. I like the design of AKG P220 shockmount better - the mic is locked into the mount with a threaded fitting, the MXL uses clamping pressure by a metal clip on the outside (press the two pieces together to loosen). The 3-way, low-cut and pad switches all end up right next to the edge of the mount, so they're hard to get to.
Put them side-by-side for the first test - recording my Taylor. Could discern no difference in sound from the two - a subtle frequency difference can be seen on a graph, but not much. I also tried a 2-mic set up with my AKG at fret 12, the MXL at lower bout, both about 12" away. I don't think the MXL picked up as much of the low end as when I have tried this method with a cheap pencil cardiode or a dynamic mic.
Also tried a mid-side set up with the MXL set up as figure 8. My room is probably not ideal for that set up - carpet on floor, and a lot of rockwool. I could hear what the MXL was picking up, just don't think it enhanced what the AKG was getting in its normal position.
On vocals, went back to side-by-side, recorded a bunch of tracks. Again a very subtle frequency response can be seen on the graphs, but very hard to hear the difference. The AKG seems to have a slight peak in the 1-2K range in comparison to the MXL which has a slight peak in the 5K-6K range. The peak I saw on the MXL spec sheet around 9K did not make itself noticed either with my vocals or the guitar recording (nothing to speak of up in that range, I assume).
Summing the two signals does have a nice benefit of accenting the 1-2K plus 5-6K range in my vocals, but nothing that couldn't be done with either mic and a touch of EQ.