I've never been a big fan of the trophy vs top four debate. At the end of the day it's apples and oranges with the only commonality perhaps being what a person might define as a successful season.
The fact is that if you take the emotion out of it, the cold hard facts are that top four is far more important. It's important financially. It is more important for club profile. It is more important for recruitment. For all these reasons it is more important for long term progression, especially if top four qualification is a regular thing - plus statistics show that the majority of domestic trophies in the Premier League era have been won by sides who were also competing for top four at the time, so number of trophies is clearly linked to quality of squad, and your place in the league, more than some realise. Plus the "prize" of CL is the right to play the game's elite.
But the thing is that the game isn't just about these things. As others have said winning is a feeling superior to all others. I've only see us win two trophies but both were very special days for me. Hell I remember 2008 vividly. I don't think the Mrs ever got a rodgering like she did that night! That elation is simply irreplaceable. It also means that for that one year, you've beaten out all the rest and remained undefeated throughout the competition.
If I had to choose I'd take top four over the FA Cup at a push, and only because the more top four finishes we have the more likely we are to pick up an FA Cup sooner or later. But here's the thing, it's a pointless conundrum! We don't have to choose. Every year we compete for both! If we finish the season with a trophy it is a good season. If we finish with top four it is a good season (especially considering the days when we'd not even be in Europe). If we do both, which is more than possible, even better! I therefore never understood why fans debate and argue this as if it's one or the other.
What would it mean to win the FA Cup? It means joy and elation. It means memories. That means it would be a good season and a great triumph for us.