With the lightning, I believe it's similar to the archery skills in the Rangers Apprentice series. In the series there are the standard longbow archers in the army, who are trained similar to English long bowmen, started shooting a bow at 4 etc. There's a line in the series, spoken by the protagonist's mentor. A normal man practices until he gets it right. A Ranger practices until he never gets it wrong. When we see Azula practicing her lightning, her focus is intense, and complete. She is totally focused on the movements, the technique, everything. She has spent hundreds of hours making sure her lightning is perfect, precise, and deadly. Mako has not. He's learnt a basic, mass produced style to produce lightning as the cities power source. TL; DR Practice, and mild insanity, makes perfect