0.6 micrometers is generally acceptable. However, it is better if you make it 0.4micrometers or lower. Most of the micro living organism are of the size range of 0.1 micron to 0.4 micron, so you can ensure no biofilm formation by adhering to the above surface roughness values.
I would always prefer EP to MP because of uniform surface finish and superior quality.
Regards,
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