S5 cost rm2xx more than S3. if buying new camera, get S5. if already have S3, dont bother.
S5's improvement over S3 in no particular order,
1. bigger brighter screen
2. "better" EVF
3. 4GB video limit
4. red eyes removal in video mode
5. faster startup and more responsive
6. hotshoe (don't bother, if got money to purchase speedlite, get DSLR)
7. IMHO, useless face detection
downgraded compare to S3:
1. burst rate reduce from 2.5fps to 1.9fps
2. battery perform worst
3. intervalometer gone
4. higher noise if compare pixel to pixel
5. weight more
6. memory card placement, cant change it when on tripod
7. DIGIC II is hackable and scriptable (i like this the best)
this is what i know based on my weeks of researchs on this two camera