Hi Colin - welcome to the forums.
I think the biggest difference between the 2 is their size. The Nikon is a fair bit larger.
I would also consider the Panasonic DMC-TZ6/TZ7 and the Canon SX200IS. A good group review (including the Samsung) can be found
here.
There are also the Canon SX120IS and SX20IS both of which are more like the Nikon P90 in size.
A side by side comparison of all these cameras can be found
here