Well , the 6.9 is a classic. You could probably find other 500E but I doubt if you'll find a 6.9 with 50K and condition that you're describing ur's is in. Moving forward your 6.9 is bound to appreciate in value as a classis same could be said about the body style. while the 6.9 is disctinctive, let's face it the 500E shares the same body style of any other W124 of which you can find thousands out there.
But at the end I suggest you should figure out whether you need the car for fun/ or show purpose. for fun i'm sure 500E would do. but to keep a classis. well. that's another story. good luck eiter way