Interresting, as usual, Del. We use all three types of salt - well, actually, four, now; we got a small bag of "grey salt" in a Christmas package. It will be interesting to find out what it tastes like in cooking. We've found that sea salt seems "saltier" than either kosher, or iodized table salt. Our box of Mortons Iodized is over a year old, and still is about half full.
Anecdote: on our fireplace hearth is a grey, semi-opaque stone that folks seem to ask about from time to time; it is about the size of a football, and weighs about five or six pounds. Whenever someone asks what that is, I pick it up and tell them to lick it - it is always amusing to see the reaction. After they get past the idea of "licking a dirty old rock", they are amazed to find it is "salty!". It is a solid crystal from the old National Chloride evaporation mines at Amboy, California; my brother worked there in the summers during his college days, as a blaster, blowing up the salt beds for removal by dragline. The material was shipped by rail to the San Francisco bay area for refining. I think he said that it contributed to regular Mortons (and other brands) table salt, and rock salt. The mines are still there and in operation, but I don't know if they are still mining "salt" there - maybe just some other sort of minerals. They used to mine potash, and bromine, and several other things, as well as salt.