All linear weight boxscore based rating metrics are very faulty - be it Eff, PER, WPs or whatever. I have no idea why are they called "advanced stats", they're boxscore compilations. It's like calling a 2 pages digest of the Moby Dick an "advanced version of Moby Dick".
NBA efficiency is particularly rudimentary, but I'm not sure if that's an advantage or a disadvantage. In any case, they're all pretty useless.