I've played in 4 cup finals now, all under the old system, but you must remember I was considered a underdog in those cups too with being a lower level than the other best teams in the competition, I can remember my first cup final in L11, playing a team 3 levels higher and 15Q more than me, I set my team up rather defensively with a view to counter attack and try to get an early lead and try and frustrate my opponents for the rest of the game, but sadly as expected they scored 3 times in the first 20 minutes and the reverted to my normal style afterwards and the game finished 4-0 but it was a respectable performance in the end. I knew I didn't have much chance but just gave it the best shot I had, I did overcome a stronger team than me in the Semi-Final to get into that Final.
As for the current cup format, You manage to make it through to the late stages you know you've got a great chance with playing similar quality teams to your team. On a old server in the lower levels you will encounter a lot of abandoned teams from 2 or 3 levels above, but because they are abandoned player morale will be low and teams not looked after, chances are that you will progress.