Ask an Aran thread.

Indeed. You have the choice of maxing 3 of the 4 skills, and you're going to be slacking 4 points total on whatever you leave out. Preference I suppose, step is very useful @ higher levels for getting in-between gaps of monsters faster to keep your combo going.

Basically, what you'd lose with Max Booster is a larger step and Max Step = Shorter booster.

However, IMO, the usefulness of max Booster over-rails max step, since Level 5 is enough for me.