The S5n is a redesigned S5i.
The S5n has a larger LCD (2.0 inches), and a larger movie mode (640x480).
There appears to be no difference in the lens or sensor, so the S5i and S5n should produce identical photos.
Here is a link to sample shots from the S5i:
http://www.steves-digicams.com/2004_reviews/optios5i_samples.html
Here is a comparison of specifications:
http://www.dpreview.com/reviews/compare_post.asp?method=sidebyside&cameras=pentax_optios5i%2Cpentax_optios5n&show=all
I notice that due to the larger LCD in the S5n, the viewfinder is gone. Most LCDs are hard to see in sunny outdoor situations. The S5i would have the advantage when shooting outdoors on a sunny day because it has a viewfinder.
.............
If you live in the USA, you may have trouble finding a S5n camera. The S5n is available in Europe and England, but I did not find a seller in the USA. Also the S5n is not shown on the Pentax USA website, but you can find it on the Pentax United Kingdom website.
...
..
.
i'm interested in buying a digi camera, and have been loking at theses two models, but don't know which one is better,has anyone got either of these cameras or info about the true image quality.Any suggestions. thanks

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic