You are going to get a ton of replies on this question. The differences between the afore mentioned striking surfaces is as wide as the day is long. Copper, high maintnence, great all round pick for raspiness and has so many sweet spot capabilities, glass, great high pitch but, if not installed right is deader then a doornail, crystal, quick response raspy and great player in humid weather and aluminum is tricky but effective for reaching out, but the trick is in the strikers. It is a well known fact that an assortment strikers, makes one pot sound like four.