Here is a link to the comparison of specifications:
Both are excellent cameras.
If you don't need a 12X optical zoom or a hotshoe for an external flash, then get the A650IS.
I want to buy a good camera but I am confused between A650IS or S5IS.
I have read few good reviews of both A650IS or S5IS.
Can one who has used/using Canon A650IS or S5IS give their suggestions?