Which is better coding style?

Is better to code
1. In a way can be readable easily on first sight but maybe inefficient
or
2. That is very efficient and short but more complicated to read and understand

My instructor (a very scary prof) always tells us to go to option #1. Yes you can still do option #2 if you provider enough comments to explain.

But if you do option #1, you will not need to comment alot about your code because your code will speak for itself because of its easy readability.

What do you think?

I tried #2 at work. Five hours later my boss taps me on the shoulder says "I know you're knew, so I won't rape you for this - but you reeeeaally don't need to spend that much time optimizing this. If I need you to do that, I will tell you explicitly." This holds up pretty generally I think.