awooga83 the supposed upsides of younger players are way over-indexed by fans. I blame FM and FIFA.
Being younger has benefits, but improvement is the slipperiest of them. It just means the club is less likely to make a loss if they sell, that you might be able to pay them a lower wage (at first), and they might spend more time with you if that's what you both want. I think its less about improvement and more about being a bit more flexible than older guys who are more stuck in their ways. There is a massive downside to that, in that they lack experience and might not really have 'ways' to get stuck in, and can therefore be ineffective. You also have to manage younger players physically to avoid breaking them and ruining their future, while older guys might be more willing and able to put it all on the line for one last hurrah.