[mormegil]

I believe that had Feanor lived he would have brought destruction on the Noldor much sooner. His impatience led to tatically unsound manuvers and combined with his ability to get others to follow him would have led to a premature war in which the Noldor would have suffered a grim defeat and their numbers would have waned greatly. Also I think the schism between Fingolfin's people and Feanor's would have been much more difficult to heal.