Gentlemen, thank you for your replies. You've given me several things to consider.
I like the flexibility that a handheld recorder like the D100 potentially gives to me because it has reasonably good onboard microphones. If I didn't care about the built-in mics then of course there are a number of field recorders in addition to the sound devices MixPre-3 to consider.
I must say that after listening to the Soundcloud samples I found that the Roland CS-10EM binaural mic headphones connected to a D100 recorded some very nice sound outdoors, with good stereo separation and surprisingly good resistance wind noise, especially considering there's no means to put a furry windscreen around them. I've never used binaural mics before, and when I did a Google search for them today I was rather surprised to find some actually shaped like human ears selling for well over $2000! But having the mics built into headphones would seem like an interesting way to record sound and monitor it at the same time, assuming the sound you are monitoring doesn't interfere with the sound you recording since I'm sure the vibrations from the headphone speakers would make their way to the mics, right?
The other Soundcloud files were difficult to determine which recorder was which in the comparisons because nothing was announced on the recording, and when viewing it on my iPhone I couldn't see any text description other than the title; furthermore, the text title lists comparison mics in a certain order, but I didn't seem to hear those mics in that same order in terms of the noise I was detecting. But the one Soundcloud file that did seem to make sense, with the mics being in the same left to right order as the text description, was this:
Ticking Clock Rode iXY, D50, D100
https://m.soundcloud.com/quisquose/ticking-clock-rode-ixy-sony-d50-d100-comparisonThe Rode mic has less hiss but it picks up less in the higher frequencies of the clock ticks. The D50 detects higher frequencies better but it has a noticeable hiss. And then the D100 as a wider soundstage, detects high frequencies well, and has the lowest hiss of them all.
I used my AKG K702 headphones and a Headstage Arrow headphone amp attached to a lightning to headphone jack adapter on my iPhone 7 to listen to the Soundcloud samples.