Canon does not have a SZ210IS.
I assume you mean SX210IS.
I can not find any actual reviews on the Nikon S8100.
I did find a lot of comments from people who have purchased the S8100.
It is a mixed bag.
Good reports and bad reports.
You can read them here:
http://forums.dpreview.com/forums/readflat.asp?forum=1007&thread=36901620&page=1
.
Which camera is better.....

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