I'll try to clear up the temperature questions as best as I can.
Anytime there is more than one variable you can only make generalizations.
Here are some of the variables.
A) Wood density. IMO with all other variables held as constant as possible wood density is the most important factor. And wood density can vary from one piece of wood to the next withing a single species. ie. one piece of American Cherry can be more dense than another piece of American Cherry. Ignoring that, and taking a species average, Alder will be warmer than Cherry or Walnut, those will be warmer than Myrtle, and Myrtle will be warmer than Ash and so on...
B) Unit diameter. All other variables held constant, there is a higher R-Value in a thicker body. But I do not believe this is a significant factor.
C) Resistor value. While the Ohmite resistors are very consistent, we toss out any that are > +/- 2% of target value and test every resistor (always have, you can see it discussed early in the PD thread). If you used the out of value resistors on either side you could expect a wider range of temperatures. I have no idea what QC protocols other use. We state ours. We want as consistent a product as possible.
D) Wall power, like resistors they can vary from one to the next (and we test them). With resistance set, Voltage controls heat output.
All the above variables, will affect either a PD, or MZ.
Internal differences of the Heat Exchangers construction and materials (and several other internal design differences) in the two products create further variables as mentioned.
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A few years ago I made some wooden tubes, never noticed anything magical about wood vs. plastic as far as cooling. After all wood is an insulator, not a conductor. Wooden tubes are neat, cool to look at, but cooling properties (of wood) seem to be over-emphasised considering the physics and my experience. Long glass tubes do cool the vapor, Pammy uses one, but you also are mixing the vapor with the air in the tube, diluting it somewhat, not something everyone is after.