Arc- is great for PvP ( crucible ) and also great for its famous invisibility trait. Solar- is what i use for PvE because it causes damage from a safe distance . //// But i switch over constantly depending what role im playing. For example arc blade is what i use for the beginning of Crotas end . But at Crota i switch of to gunslinger its better for oversouls and taking down the sword bearer. I hope this helped!