I always took that scene to indicate that while the Creator allows access to an unlimited power source that could extend life if used moderately, the Dark One allows access to an unlimited power source that would drain your life while making you want to use it more.

I didn't take it to indicate that the Dark One was more powerful than the Creator; only that the Dark One was more willing to destroy or corrupt people it gave gifts to while the Creator gave you a measure of it's unlimited power, but not enough to automatically lead you down the path to destruction.