Remathilis
Legend
Here is where I drew the line on the two terms.
I considered the idea of every class introducing himself as "I am Bob the Y". When I did, I noticed some classes felt like things people would call themselves. This self-identity was what I called professions.
A fighter might self-identify as someone who uses weapons/armor, but he would call himself a sellsword/mercenary/guard/bouncer first. Fighter describes what he does, not what he IS. Fighter explains his archetype: someone who uses weapons/armor well. Rogue falls in a similar category; a rogue can be a cutpurse, diplomat, con-man, cat-burglar, acrobat, or any dozen types of skilled character, but he will call himself that before he refers to himself as a "rogue". (Ironically, "Thief", the original term for the class, describes a tighter profession. It also assumed a lot more about his origin and desires, which was a common complaint that lead to the renaming of the class).
Compare to ranger. A ranger isn't just a woodsman. The class assumes a certain belief and training required. This was more true in earlier editions which granted him spells and forced him to be good-aligned. Bob introducing himself as a ranger means something that Joe introducing himself as a fighter doesn't. This is similarly true of monk, bard, or druid (just to name a few) where a certain assumption of training, ability, even world-outlook are assumed by the class.
The caster classes are a little fuzzier. There is no-doubt that "magic-user" is archetypal, but other arcane casters (mage, sorcerer, wizard, warlock, witch) could be both. I tend to assume someone like a wizard would self-associate with that title merely because it explains his need to use a book to learn spells (compared to nearly all other casters in the game) but that's not given due to the fact that most of the arcane classes are pretty much synonyms of one another. Clerics are a bit more concrete; it implies a priest without using that word but it still can be seen a fairly archetypal.
As WotC added new classes in the 3e and 4e era though, they dove squarely into archetypal. A few could still be professions (samurai, ninja, knight) but a lot were descriptive rather than professional. Spellthief? Duskblade? Beguiler? Would those words even HAVE a meaning in the world like Assassin, Paladin, or Bard does? This also explains the infamous hatred Warlord earned over its name; its archetypal (referring to the warrior-leader archetype) but many chose to see it as professional (and dislike how it implied command over some area of land and/or an army).
I think in the end the main core classes (fighter, cleric, mage, rogue) were supposed to be archetypal while later classes (bard, druid, paladin, ranger, monk) more represented specific professions. Along the way, the two bled into one another. And like many, I think there is room in D&D for both.
