The CM11 is even lighter on resources than the stock Android. It also brings plenty of useful features without you needing to install them separately like Torch, ability to turn on & off features straight from notification bar which is extremely convenient. You can also add more entries of your choice in said bar, e.g. network data preference (2G or 3G). Not just this, but the CM11 comes with a beautiful File Manager out-of-the-box which even puts my paid Solid Explorer to shame; although the UI is very identical. You'll definitely feel the difference once you start using it yourself. Even tiny things like changing hostname alone make it a worthwhile practice.
I also agree with what @Durteedee
said, GravityBox should bring many of CM11 features to stock Android if you don't want to deal with flashing and stuff.