Power settings for lecture

I regularly use my macbook in lectures to take down notes as the lecture reads something important out. Quite often during the lectures I may write something down then the lecturer will go over something for a period of 5 mins or so where i will not be using my macbook.

For these periods of inactivity, is it best just to set my power settings up so the screen goes black and turns off or actually sleep the macbook?

At the moment i find that sometimes my macbook goes to sleep in these periods and i have to re awaken it from sleep. Would doing this repetidly waist more battery than just having the monitor turn off?

What does turning the hard drive off when possible option do? does it make much difference?

just turn the screen brightness down, no need to put it to sleep only to wake it up a couple minutes later

Yeah, just hit the brightness buttons.