Chapter 9: Cinnas advice definitely helps more. She finds haymitch's advice kind of offensive.
Chapter 10: The capital literally and figuratively changes people. He dosent want to die as this screen personality. He isnt entertainment. He is a person. What could change Peeta is his "act" for the hunger games and death and killing others. That could most definitely change a person and Peeta does not want to lose himself.
Hope this helped :)