The differences in noise between the portable recorders is pretty slight - under real-world conditions it would be negligible in my view. The NT4 is obviously significantly quieter.
In terms of frequency response and stereo image, again, it's perhaps a matter of what you like. The differences are subtle. I keep getting the feeling that the H2N is bass light but that could be an illusion. I've been listening to these samples lined up in Reaper each on its own track and soloing between them while playing back, including short looped sections, till I never want to hear a guitar again! (Even as well played as in the samples!!). I suspect that if you made a compilation of the four, or even better just the three portables, nobody would be able to say which bits came from which recorder. I also did some analysis in Adobe Audition but nothing in particular of note emerged from that.
I may have the chance next week to try the H2, H2N and Sony M10 and perhaps a Suplux S502 mic all together during an orchestral rehearsal in a church. That would highlight the stereo imaging quality of these devices perhaps.
Fantastic work on the video. Very nicely done and a great help to others.
Thanks again, sir.
The M10 is the joker in the group you mention - the mics are omni which means there is basically no stereo image as such with the two mics so close together. The Zoom recorders don't get much credit in the reviews I've read for their cardioid mics and stereo image, but the standard config for these small recorders seems to be a pair of omnis less than 2" apart - a recipe for two channels of mono.
On the other hand, if the capsules are decent and the electronics allow it, the bass from the M10 should be noticeably different and more natural. The same engineering that makes mics directional makes their bass response problematic compared to omnis.