In Australia at least, "diet-something" is probably more associated with "healthier-something", though the term is pretty much exclusive to softdrinks. "Light" is used in all other food products (or, as people would have it, "Lite").

In soft-drink terms, you'll find the word "diet" be associated with "tastes like shit". Luckily for me, my sense of taste isn't as picky as my sense of sound.