They have different designs. Solar is a witch killer. Fire shields, usually attacking from range, and heavy impact. I also really like high impact low charge rate for when you can't get many hits in. Like if you have to peek out from behind a wall for a second, you want that 1 attack you get off to have max damage. Arc is for melee. Closer range, fast charge so enemies stay off you. Great for thrall. Knights, captains, blade vandals.