Beyond the dual core, the RAM is the next best reason for me for this phone. I start up near 500 and can run anything I want and it never skips a beat.
I use the System Info Widget to track things and I have never dropped below 215 with a ton of crap running!
Samsung Galaxy S4 (SGH-I337) Black Mist (32GB)
Samsung Galaxy Note II (SGH-I317) Marble White