RE: Why is lighter...."better"?
If you hunt out west a lot, you'll find yourself tracking very long distances. As time goes on, carying that bow just makes it feel heavier and heavier. I would say this is primarily why someone would want a lighter bow. Heavier bows may help with accuracy to a point, but most of the modern bows (light or not) are very accurate anyway. So I think it basically boils down with starting out with a lighter bow in the first place, because by the end ofa long out west hunt that bow is going to feel 2-3 times heavier.