Whats the difference between glucosamine hcl and glucosamine sulphate?

i wanted to buy glucosamine hcl today, but my rather large pharmacy didn't have it...all they had was the sulphate grade. I was told hcl was the best and to stay away from grades like 2kcl or Nacl.....how do the above 2 grades compare? are they the same? just 2 different kinds of carrier salts? or is one better or more potent than the other?