It's got to be worth a few points per season, otherwise SI would not have bothered developing it.
Having said that, I'm too lazy to use them, and I'm still doing well with my Bognor Regis game, got them up to League 2 from the Conference South so far.
Possibly though it becomes more important to single particular opposition players out when you play at the highest level due to the ability of the likes of Henry/Ronaldo/Gerrard etc to win a game single handedly if allowed to do so.
Down in the Conference, even the best players are rubbish