I find crystal to be able to reach much higher pitches in the front end ( listen to a Halloran Crystal Mistress ). Glass to me has more of that old school low pitch raspy old hen capability. I also feel glass takes a little more work to keep it calling well. I find I have to scuff it quite a bit more than my crystal calls. Which one is the best will always be determined by the birds you are hunting...and in what mood they are in during the exact time you are calling to them....and that is subject to change at a moments notice and without warning.
