I have both the Dixon the MK (though slightly different models) and they’re both among the most ergonomic Low Ds. The Dixon is perhaps the most ergonomic Low D, but in quality of timbre, and volume, and tuning, the MK is IMHO clearly superior to the Dixon.
If you want all the details, here’s a review I posted in another thread a while back (the review of the Kerry Optima while it was on its USA tour)
Susato keyless with angled neck
Dixon all-plastic two-piece conical bore
Reyburn alloy body/maple head
Reyburn alloy body/polypenco head
Burke Pro Viper alloy
Kerry Optima alloy with red plastic top
MK tunable (like the MK pro but made before that designation was used)
Tuning:
All of these whistles have an accurate scale and can do the oxx ooo crossfingered C natural well. This Burke, and some other Burkes I’ve owned, have a curious tuning anomaly, B being a tad flat in the low octave but spot-on in the 2nd octave.
Octaves, flattest 2nd octave > sharpest 2nd octave:
Dixon > Reyburns/Burke/Susato > MK > Optima
With the Dixon the low octave must be rather underblown. The Reyburns, Burke, and Susato have the 2nd octave in the (for me) most natural place. With the MK you must strongly blow the low register and be careful not to overblow the 2nd octave but with practice it’s easy to keep the octaves in line. This Optima has the sharpest 2nd octave of any of the Low D’s I have to hand. In fact it’s quite difficult to blow the low octave strong enough and blow the 2nd octave softly enough to keep the registers in tune; I have to blow the low notes right to the verge of them beginning to flutter/break (their tone becoming less than optimal) and blow the 2nd octave right at the verge of falling to keep the octaves in line.
Volume:
Without being able to measure volume, it’s more of an impression than a scientific reality. My overall impression, playing a tune that mostly dwells in the low range, is:
Loudest > Softest
Maplehead Reyburn > MK > Burke/Susato > Optima/Polyhead Reyburn > Dixon
Bottom D strength: There’s a big gap, with Susato, Burke, and the Reyburns having very powerful Bottom D’s, and the MK, Optima, and Dixon having weaker ones.
Evenness in strength in the Bottom D/Low E/Low F# range:
This is something I really become aware of when playing tunes that dwell down there. You go to play E and it breaks because it can’t take the same pushing its neighbors can.
The MK, Optima, and both Reyburns are remarkably even and you can play down there with confidence. The Dixon, Burke, and Susato have E’s which are considerably weaker than their neighbors.
Air efficiency:
A little difference, a couple seconds in how long you can sustain a note, makes a huge difference in how you phrase tunes. I prize an efficient instrument on which long phrases can be played, and you can just play without having to put in frequent gaps.
Most efficient > least efficient (measured by how long I can sustain G in the 2nd octave):
MK > Susato/Dixon > Burke/Optima/Maplehead Reyburn > Polyhead Reyburn
Timbre:
This is of course entirely subjective. The Susato and Dixon have pure colourless timbres. The Maplehead Reyburn is pure but adds an NAF-like resonance. The Burke is pure but adds a bit of dirt/gravel. The polyhead Reyburn has a unique foggy NAF-like presence. The Optima and MK have the most gravel/dirt. The MK combines this dirtiness/graveliness with a strong ‘core’ in a way that sets it apart from the others.
Comfort/ergonomics:
As I play Low Ds more and more I’m realizing that upperhand comfort, for me, seems to be hugely impacted by fairly small differences in tube fatness, hole spacing, and hole size.
The Dixon with its close, small holes and skinny tube is by far the most comfortable for me to play. The Susato and MK are next, with narrower-than-average tubes and smaller-than-average holes. A fat tube and far-flung big holes make my upper hand less comfortable.
Tube OD:
Susato .89 > Dixon (at C# hole) .91 > MK .96 > Reyburns/Optima/Burke .985
Upperhand finger spread/hole size measured from edge to edge, smallest > largest:
Dixon 3.12 > polyhead Reyburn 3.24 > Susato 3.28 > MK/Optima 3.31 > Burke 3.33 > maplehead Reyburn 3.46
(The differences might seem small, but the difference in upperhand comfort for me between the MK and the maplehead Reyburn is huge.)
Lowerhand finger spread/hole size measured from edge to edge, smallest > largest:
Susato 3.16 > Dixon 3.18 > Optima 3.24 > maplehead Reyburn 3.25 > MK 3.26 > Burke 3.36 > polyhead Reyburn 3.4
Odd, isn’t it, how some whistles have among the biggest spread in one hand and the narrowest in the other. Would be nice to have the upperhand spread of the polyhead Reyburn and the lowerhand spread of the Optima. (The Susato’s placement is obviously not optimal tonewise.)
, but the V4 is not on my radar as it has not come up for easy fingering in my research (nor for the opposite, admittedly). Reckon, the breathing requirements might be demanding for a beginner?
? Everything is relative, you know. (Well, even measurements, if we think it through …)