It's recognizability. Let's not kid ourselves. Virtually anybody recognizes the distinctive shape of the Mustang. Even non-flyers. So onlookers will immediately recognize your plane, which automatically eases the conversation, and eliminates most of the "silly-question-hour". Not to mention the high esteem your co-flyers will hold you in, owning a piece of aeronautical history.
For me, it's all that, and more. My father used to be a member of the Royal Dutch Airforce (back in the early, early fifty's), and with NATO rising, a group of Dutch pilots were send of to the States for further flight training. My father was deemed a good enough pilot (or reckless enough) to be included in this group. He first re-trained on the Harvard (or Texan for some), and after that went on to the Mustang. No small feat for a skinny, 163cm tall guy. Actually, the minimum height was 165cm, but I guess the recruiters had to meet a quota, so he was "in". Every military plane he ever flew (with exception of the Piper Cub I think) he had to fly with a cushion under his parachute...
That's him in the picture of "Finger Flight" below. Third from the left. But you could figure that out all by yourself...
So, yes, the P51 has always been on my "to have" list. And here it is...