Nick and Cait are the go-to companions completely for their perks and dialogue. The Railroad is good for the Ballistic Weave armor, BoS for the Power Armor, Institute for the weapons, and The Minutemen for repeatable XP quests. xD
I guess they all have their own advantages. The Institute just creeps me out though. Their base has a whole "You've been playing too much Mass Effect" thing going on. xD