Skills vs Levels

I have a question regarding player’s special skill, like free kick specialists and so on. I know that if you have 2 players, same skills and one is specialist in free kick, that one should perform free kicks. But what about if I have 2 players, one has attack skills at lvl 29 and no specialty and the other is free kick specialist but skills at lvl 25.

Basically my question is, how many levels of skills is worth specialty - sort off. I can imagine that specialist at lvl 25 can't be better than not a specialist but lvl 44.
Can someone explain me this? Probably goes same for all skills, like penalty, corner, ...

Regards,
One

Basically a player with a special ability is one Level/Star better when the special ability triggers, for example when he is a free kick specialist, it triggers when shooting a free kick.

OK tnx, that was the answer to my question - 1 star better.
4* Free kick specialist = 5* (no special skill) at Free kick performance.

That's ok. Thank you.
BR
OneI