User blog comment:Shaw Fujikawa/Just CC them!/@comment-213.114.249.127-20121004165710

Another thing you need to keep in mind is how mobility effects the effectivness of CC. Ex if you root ahri for 2 seconds you have hindered her form using her ultimate for two seconds. Basicly you have denied her about 1500 units of space she could have traveled. While if you root say, darius you will only prevent him form traveling about 600 units. This way, hard cc is more effective on mobile champions.

As you mentioned, cc is also good vs high damage low survivability targets, and bad vs high survivability low damage target.

If you stunn a 6 item ashe for 2 seconds and during this time deal 2000 true damage you will be able to take 100% of her health and prevent her form dishing out about 2000 damage.

If you cc rammus for 2 seconds and deal 2000 trude damage you will take 66% of his health while preventing him from dealing mayb 400 damage.