I don't care if there's any difference at all between +2 and +3, I would still upgrade it to +3. I guess it's some kind of completionist obsessive-compulsive type thing. It would bug me knowing I can still upgrade an item, even if it only changed names from 'balanced" to "masterwork."
Also I have retired many times and I rarely trade anything other than one +3 for another +3. Any loom points I get from retiring I save to make +3 items that are rare or never available on the marketplace. I don't think the marketplace is going to change much for me.