Feanor is from a time before war and he is the first to make design of insruments of death, he was nothing more than a angery, genius, craftsman.....Fingolfin on the other hand is from a time were war and death has become a regular thing and he has the bonus of 1000s of years of the adaptation of the early noldor creativaty on top of warmanship he is a king and a warroir not just a craftsman like the early noldor. Fingolfin would kill him stone dead.....but think about this....what would happen if Feanor had lived to the time of Fingolfin's prime, who would win then maybe Feanor? imo