These scenarios do not really warrant comparison because they have entirely different goals. The goal of scenario one is to complete a task, and anything learned in the service of this goal is a "fringe benefit". The goal of scenario two, on the other hand, is learning, and the completion of the actual assigned task is merely a means to this end.

So while reinventing the wheel may be a necessity for learning, it's an impedement to efficient and correct implementation of a task. You're comparing apples and orangutans.

   MeowChow                                   
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