As regulars here know, I’ve been on a big Quest for the best Low D I can find for around three years now.
I sure haven’t tried them all. I have owned Low Ds by Copeland, Burke, Overton, MK, Susato, Reviol, Howard, and Kerry (that’s all I can think of at the moment) and have tried several other makes (including a Sweetheart Low D/flute combo).
Now you’re asking about the “easiest” and mention two specific areas, breath requirement and finger stretch.
The finger stretch issue usually revolves around the placement of the sixth hole from which E emits. Low E is often the Achilles’ Heel of Low Ds, the weakest note. Keep in mind that the placement of that hole is a compromise. The acoustically correct thing, which would result in a Low E that’s just as strong as Low F# and Bottom D, would be to have a large hole, the same size as the F# hole, down halfway between the F# hole and the open end of the whistle. But almost no one could play a whistle like that.
The most ergonomic placement would be a tiny E hole way up close to the F# hole. But this would result in a feeble Low E, that could only be blown very softly or it would break to the 2nd octave.
So, the size/placement is a compromise, unless you have a key for that note like some Susatos have. I’ve played a keyed Susato Low D and I didn’t like the feel of the keys at all.
Most Low Ds have about the same placment of that sixth hole and reaching it shouldn’t be an issue if you use the “piper’s grip”.
Anyhow, after playing a lot of Low Ds I ended up liking the MK and the Burke the best. For the full review see the post I did a while back called something like “Low D review (road test?) Reviol/Burke/Susato/MK.”
I’ve ended up liking the MK a bit more than the Burke due to several small factors: The air travels through the MK a bit slower so that I can play longer phrases on a breath, the Low E is exceptionally powerful, the narrower tube and smaller holes make it a bit more comfortable in the hands, and ornaments pop out of the MK a bit more clearly. But, the MK lacks the Burke’s amazingly powerful Bottom D.
There’s a video of my playing those four Low Ds:
http://www.youtube.com/watch?v=fkL06uOtZQc
Don’t overlook the Susato. It has a slim tube and smaller holes like the MK and has easy breath requirements. It has a great Bottom D (just almost as good as the Burke’s) and sweet high notes. I just don’t like the actual timbre/tone as much as the MK’s or the Burke’s.