Any kind of long storage of garlic will change its flavor somewhat because the allicin, which gives garlic its fresh, biting taste, dissipates rapidly when the garlic is cut, crushed or bruised. Supposedly, dried garlic retains this better than other preservation methods. (See
A Primer on the Chemistry of Garlic.) However, I see little point in buying fresh garlic in order to dehydrate it, since commercially dried garlic is cheaper and better than what you can do at home. It's an option if you have surplus homegrown garlic, though.
Since cooking dissipates allicin anyway, garlic you intend to cook can be preserved other ways.
Chop in a blender or food processor with a little water, freeze in ice-cube trays. (Dedicate trays to the purpose of freezing smelly things like pesto and garlic. Don't use them for ice.) I have also heard of freezing the whole cloves, tightly wrapped, but I haven't tried it.
Make garlic butter. Freeze.
Make pickled garlic. (
Recipes.) Or just cover the garlic with vinegar. Keep refrigerated.
Pan roast the garlic in oil to cover over very low heat until soft. Puree. Refrigerate up to two weeks or freeze in ice-cube trays.
Extra garlicky things to cook:
Shrimp DeJonghe, skordalia, garlic soup.
I think the peeled garlic available in the produce department at Korean groceries is better than the Costco stuff, but that may just be because of higher turnover.