I cannot rank them on the basis you outlined.
Easy of use and cost effective is a relative thing.
It depends upon a point of view.
All except the Nikon S5 produce good clear photos.
Sample shots from the S5 show out of focus on one edge.
I don't know about the Nikon S9, it has not been reviewed as yet.
And I have not seem sample photos from the S9.
The Casio Z750 has manual controls and will have more settings to deal with.
The Canon, Casio and Sony have viewfinders which will be very helpful on bright sunny days.
The Sony W50 has the lowest price.
Here is a look at their specifications:
Please rate these cameras:
1. Casio Exilim Z750
2. Canon SD600
3. Sony DSC W50
4. Nikon Coolpix S5/S9
Please rate them based on the following 3 requirements:
* Easy to use.. Manual features not going to be used much.
* Good and clear photos.
* Cost effective.. This camera is to gift a person who has very little knowledge on Digital Photography and would take just casual snapshots.
Your rating would help me a lot in gifting this to the person on his B'Day!!