System resources!!! KK is designed specifically for midrange devices, so uses less memory, etc. I've ran stock 4.2, stock-ish 4.3, GPE 4.3, and Sense on top of 4.4. If you want the least memory used(read:more reserve for games etc.) Then a GPE 4.4 is your best bet. My device before was a Galaxy Nexus, so I stick to Sense, mainly for the Beats audio(software) and the much better Sense camera. IMO, an inverted 4.4/Sense 5.5 rom, like the Eclipse 1.5 release, is not only greaaaaaat for battery life, but having everything blacked out is delicious. Hope this helps.