Such a dismal difference in sizes. If they are the same size, then they can be rotated to maximize tread wear; pick the 275 if the front can't take 285.
What car is this that it needs an unusual combo? Also, tires in that size range aren't inexpensive unless they are no-name brands.
What does your definition of "beat on the car" entail? Road course, autocross, drag, drift, dirt rally, spirited driving on twisty roads?