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?

Look at this article about the best way to code CSS for web optimization.
http://www.websiteoptimization.com/speed/7/

I just find it hilarious that everything it list there is the TOTAL opposite of what a normal programmer/scripter should do.