I don't have any experience with really modern engines, but as far as I know, the GE CF6 engines are one of the only engines that use N1 as the primary power instrument. The RB-211's, JT3's, most pratt engines, all use EPR. I'm not going to second guess the engine Engineers, but they probably know whats best. AS far as reliability goes, most planes can be dispatched with an EPR gauge in-op, and use the N1 as the back up. During engine monitor coupon research, engine efficiency can be determined by analyzing all the parameters;ie, fuel flow and then engine thrust. Its a way to accureatly determine specific fuel consumption and relate that to engine life! EPR is Good!