I personally use hello as my daily driver for sms messages, its really clean looking and fast. Also it has some minor theming options you can choose. The other 2 apps I have played with are 8sms which is a stock kitkat sms app. (I have a s4 so I was stuck with the touchwiz version until I started with hello). The other option I would suggest is GO SMS Pro. (it's also free) but that has a TON of themes, so if you like to change the look without changing the app, then go with Go sms pro.
Hope that helps!
-Phant0m