Why Eddie had to beat Vince
Eddie, at some point in the movie feels the need to beat Vince. It consumes him. The question is, why? Ego, pride, a drive to prove his generation? Age plays a huge factor in the film.
Eddie was Vince. He sees that. He is jealous. Jealous and sad at the same time. There are scenes where Eddie looks ponderous, alone--he's reflective of his youth and then there's Vince, his younger self, there in front of him and it saddens him, makes him realize that he's old and there isn't much time left. Mortality plays a part in this this, Eddie knowing that the end is near.
I believe beating Vince is the key to making Eddie feel young again...for the last time.