A HUD, when used correctly, might increase your BB/100 by AT MOST 2bb/100, which is quite an investment when you play a lot of hands. I'm not a HUD fiend, and I think that people use their HUD improperly, by changing their default strategy based on not enough information. Interpreting a HUD incorrectly can lead to bad plays, so there's that. There have been many times, however, where I've made correct Hero calls because of the stats I've had on an opponent. My 3-bet game is pretty dynamic depending on villian's 3-bet an Foldv3bet percentages.
I'm more of a fan of the DB which comes with the HUD, and the various features that it has. For example, being able to filter all your hands where you were check/raised on the flop is quite cool!
I have PT4, HEM2, DriveHUD, and Jivaro (Don't ask me why I have no many), and I think they all have their strengths and weaknesses, depending on what you're looking for.
tldr; Yes, you need a HUD to