Thank you.American Heritage Dictionary: A distinction usually means a slight difference in detail between like or related things, determined only by close inspection. Also it is subjectively determined rather than palpable or factual.
Difference is the most general. It encompasses all the meanings of synonyms like dissimilarity and variation, unlikeness, etc.
So with less and fewer they pretty much hit the mark with distinction according to the above description. They are like and related, etc.