JMB,
I know some people who have been using a Wagner moisture meter but don't ask me which one. I do know they are very accurate meters on the high end spectrum. Their prices are in that range too! I guess it all depends on how accurate you want to be. Of course if you saw and plane your own timber you could use a pin meter. (for accurate measuring with a pin meter you'll have to drive the pins not just a bit, but as far as you can in the wood in my experience, it does give a different reading) I am aware you being able to use a Felder combo planer from a friend from a mate [laughing]) But if you rather use planed, ready to use material it may be wise to use a pinless moisture meter in order to not do any damage that could be seen in your finished product. But getting an accurate meter is expensive (especially the ones one uses just for wood and not just any material!) I though haven't ever heard about any of the other meters you mentioned so I can't say anything about them whatsoever. Myself I use a cheap Stihl meter (don't laugh!) and it allows me to measure in different lengths of my own (not yet dimensioned) sawn timber and gives me a good overall indication of the moist content in the wood. The end grain of a board obviously gives a lower rating then when measuring somewhere halfway a four meter 5 centimeter board in its face grain. It all depends on your needs!