use the $user variable if you are going to call auth()->user()** more than once.
why ? .. think about it.
lets say that in a function you have a call to atuh()->user()->* (where * is whatever) ... well ... how PHP will resolve that??
It will go step by step (-> by ->) ... so ... now imagine you have more than one call to auth()->user()->** , well , PHP will have to resolve those expressions over and over again, .......... if you are looking for performance ... use the $user variable containing auth()->user() result inside it.