Upgrading is the more expensive option. But it comes with the perks of requiring just 5 levels more instead of 10 levels for a new uncommon skill. He will also retain half of his proficiency in the upgraded skill. His power will experience a massive boost since uncommon skills are more powerful than common skills.
However, he went with getting a new skill. It is not because he can't afford the cost of upgrading the skill. He just wants to increase his versatility by getting a new skill.
He got Quick Strike. Unlike Power Strike, Quick Strike focuses on the speed of an attack. It makes his attacks too fast to block. He opted for it over Double Strike or Reinforce, which would make him more difficult to kill.
