If comparing spyder gears, then an enlarged pic of the mugen spyder gears (MUGC0230), seems to indicate that they are not machined.
http://www.amainhobbies.com/product_...pider-Gear-10T
Various materials may be used by different manufactgorers, but I haven't seen any spyder gears that appear to be machined. If comparing ring and pinion gears, the Mugen 5T and 6T use spiral cut gears. Hardly a fair comparison. Use the HB spiral gears and things are more even.
BTW, my Fioroni is working great on my JPX.21