Had a chance to compare the Naza M to AMP 2 this weekend and wanted to share the experience.
The comparison was done on two similarly sized custom built quads at ~24" span running the same props, motors, PDU and ESCs. The Naza quad had a Go Pro and Fat Shark FPV 5.8Ghz Transmitter and weighted in at about 3.1 Lbs. The APM Quad (mine) had no additional equipment besides a Sonar and it weighed about 2.75 Lbs.
In general both performed very well with a nod going to the Naza in Loiter, RTL and auto landing due to what appears to be a better GPS. Clearly APM has auto mode and Naza does not.. for the price the APM appears to be a solid value.
As expected both quads were equally stable with no real noticeable difference in stability. The only big difference was NO TUNING on the Naza... it just worked out of the box.
The Naza quad had a noticeable difference in loiter stability and accuracy. Granted my quad my not be tuned perfectly but the Naza held its position more accurately and with less twitching in the wind to do so. The Naza's corrections to the wind seemed to be invisible.. where the APM corrections were noticeable in both pitch and prop noise.
We did a RTL comparison taking off from the same spot and flying about 100 yards away at about 35 feet. The Naza returned to the exact spot of take off. APM got within 10 feet (see below).
Testing the auto landing during RTL..... the Naza descended from 35 feet in what appeared to be about 5 foot increments. It was a very controlled decent. It landed perfectly on home and shutoff. As mentioned the APM quad hit the launch point within 10 feet. Its decent to landing was steadily and constant. When it touched down it then proceeded to skip around on the ground and went another 10 feet from its landing point before shutting down.
The Naza has no autopilot. I finally got all the gremlins out of my APM and flew several successful missions which was very cool.
APM is ~$200 with GPS and Autopilot
Naza is ~$240 + and additional ~$160 for GPS. = $400
Simple comparison, IMHO: open source or closed source.
I'll take open source any day of the week. I have both and I can find no specs for anything to do with anything DJI touches.