The HP CH is 0.30mm but I will modify it to 0.20mm which is better to make details HP CH 0.20mm or CM C plus 0.23mm ?
The Micron is a better brush, but that does not mean that everyone that picks it up will use it (or be able to use it) better than the HP-CH, with a .3, a .2 or whatever. An individual may find that for them, the Badger Sotar, or Badger Extreme Patriot is the brush that gives them the ability to produce the finest details. The Micron is still a better brush
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To be specific about answering your question - The Micron uses a different head system, and nozzle set up than the HP series. The way that the air is channeled through the Micron gives it the ability to produce a finer atomization than that of the HP series. In my opinion, the .23 Micron will produce a finer line than the .2 HP series brush. There is more to it than JUST that though - the Micron has a better trigger, tighter tolerances, etc... The deal with the Micron is that it requires the user to be a bit more diligent about paint reduction, air pressure regulation, and technique to take full advantage of. Not everyone gets along with them.
I have an awful lot of brushes, more than 60 now. Not one of them is the answer to every question
. I have produced some of my most pleasing work with some of my most inexpensive brushes... A person does the best work they are going to do with the brush they feel most comfortable using.