If your reason for buying kosher salt is culinary rather than religious or ethnic, there is only one brand to consider, Diamond Crystal, from the U.S.
More common is Windsor kosher salt, and much less expensive, but it meets the religious standards.
Diamond Crystal is derived from a unique open crystal in Arkansas, and is well suited to cooking and serving foods. It doesn't have any other features better than Windsor, just the shape and texture of the crystals.
Here is a link http://www.diamondcrystalsalt.com/Cul...
I buy mine at Diana's Seafood
2101 Lawrence Ave E, Toronto, ON M1R, CA