as i said ask any birmingham fan was their glory for the greater good of their club
well, I don't think it's straightforward. A cup win is a day at Wembley, memories, a cup final that fans can replay for ever, an addition to the club honours. It's also a stepping stone for a club that hasn't won anything for years as it can be ticked off the target list and the club can start working to the next, higher target.
Also, for a team like Birmingham, rather than just fighting relegation every year surely it's better to win a cup. Even if it means competing in the championship for a bit where they might at least be near the top so will feel better too.