I'd have to say that E would be a lot worse for you - mentally speaking. Coke can fuck your nose up, but doing it once or so a week in relatively low doses (1/2 to 1 gram for the entire week) probably won't mess with your head as much. As for one or the other, I agree with most people - MODERATION. Anything, if done habitually, can be potentially harmful and have long term effects.
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"If we knew ourselves perfectly, we should die..."
--Albert Camus