It seems Tizen can run extremely smooth even on hardware that's very lacking. I'd really be interested to run Tizen on a old S3 or S4 if a port was possible. I like how the scrolling is very responsive to the touch movement. It's almost immediate.
http://www.sammobile.com/2015/01/19/video-tizen-appears-quite-fast-and-smooth-even-on-low-end-hardware/
http://www.sammobile.com/2015/01/19/video-tizen-appears-quite-fast-and-smooth-even-on-low-end-hardware/