To me, in this game the main benefit of a good cup run is to Enthusiasm...obviously that's only a benefit if you PIC. I don't really train youngsters, so I can compete without messing up training. The only detriment is to game shape, since I overwork my starters.
In hattrick the draw isn't random -- the highest seed plays the lowest, and the seeds are reshuffled after every round, so if you pull an upset, you know you're going to face an even tougher game next time out. But the underdog hosts and gets 2/3 of the gate, and the money is substantial, as well as the gain to Enthusiams, if you Take It Easy every time.
I like the randomness of the BB cup draw, since if you win one tough game, you might get lucky and get 2 more easy ones. I've been fortunate the last 2 seasons, and its made a big difference in my league performance, though I wasn't so happy when once in the season's first week I lost all 3 games. My attendance never recovered.