Diamond cut end mill surface finish

I've been milling a lot of g10 fiberglass and have always used 4 or 5 flute 1/8" carbide end mill with 27k RPM, I get a get a good surface finish but they don't last long milling 3/16" material ,from reading around people recommended diamond cut or PCB because they tend to last longer .my question is what is the surface finish compare to am am using and if you guys have any tips that could help. Any info is appreciated .

PCD WILL last longer... great surface finish. Only problem is that they are EXPENSIVE. I bought quite a few when I could, check eBay...