Originally Posted by oldcoot
Kosher products are supposedly more pure.
This is a very very common misconception. Kosher foods have absolutely nothing to do with their purity or how healthy they may or may not be.
As for salted vs. unsalted, I prefer unsalted. I do not agree that using unsalted enables better control. The amount of salt used in butter is very small and would not generally be noticed in most cases. I use unsalted because I like the taste better.