[ILLusion]

umm... i can't really answer that question. it's a subjective sound. the tonal qualities are different. and I don't have any instruments to measure the sound. I just know the high pitched "sewing machine" isn't as bad with helical gears.

The difference between the angel silent head set and the systema... i'm not sure how you want me to answer that. are you talking about how they're designed? They're both designed on completely different concepts.