DL and DR = Defensive Wall
DC = Aerial Defender or Defensive Wall
DMC = Aerial Defender or playmaker
MC = Playmaker or dribbler
ML/MR = Playmaker or corner specialist
AML/AMR = Corner specialist, Free-Kick specialist or Shadow Striker.
AMC = Free-Kick specialist or Shadow Striker
ST = One-on-One scorer or Free-Kick specialist.
* Free-Kick SA is amazing but only train it on players that will be taking free-kicks, or it will be a waste. Same goes for Corner specialist.
This all said, high skills > Special Ability.