If you were a warrior you could go with a mail item with more strength (or in the case of your druid, cloth with more intellect) UNTIL you reach level 50. That’s when you get a passive 5% bonus to your primary stat, but only if you’re wearing the kind of armor that you’re supposed to.
For example, if you wear only plate on a warrior, you’ll get a 5% bonus to strength, but only if you’re wearing only plate. If you have a few mail pieces, you won’t get that bonus.
5% might not seem like much during the low and middle levels, but it makes quite a difference at max level.
So; You could go with the non-intended armor if it has better stats, but only before you ding 50!