It was really very difficult for me to choose any of the two truth seekers: Zoroaster and Buddha. None of their answers to the above question convinced me completely. But here are some ideas I liked and picked up from both religions.
First of all, I completely agree with Buddha's opinion that the reasons for evil existence in the world are people, their cravings and desires. To my mind, there is no any "black angel" sitting on your shoulder and tempting you. The cause of evil and suffering is very trivial: people want something they can't achieve and become unhappy because of that. Moreover, a human being can't ever stop: you want more and more even if you have enough, you make other people suffer (make them unhappy) in order to reach your personal goals (to be happy yourself), and sooner or later you're punished for that.
The second idea I liked in Buddhism is the idea that there is no any supreme power punishing us for wrong deeds. In my opinion, people themselves are responsible for their future – any bad and wrong action leaves a trace in your karma and every fraud you've done to others returns to you like a boomerang. On the other hand, the idea of freedom of choice in Zoroastrism attracted me very much. No one is an ideal, everyone is born with something good and something bad in character, and it depends only on a person which part will predominate, which way in life to choose. But Buddha's idea of nonattachment and nonmateriality seems silly to me.
To my mind, you're more useful when you don't try to escape from the world. Both Zoroaster and Buddha agree that people ought to live a good life, a life of "pure thought, pure words and pure deeds" (as Ahura Mazda says), but Zoroaster's way to do that seems more reasonable to me. You bring more good to the world helping other people to be happy rather then sitting somewhere …