Really, what is the difference? Both a very short with a rigid structure so the poet is forced to pick words with exacting care and can't meander endlessly ala Longfellow's Evangeline, and limericks have the added challenge of a specific rhyme scheme. That makes it even harder, to us.
But maybe the common non-advanced use of limericks has an advantage: even non-poets are familiar with the form because of their very ubiquity. This makes them much more accessible to the common person and gives the advanced poet a stealth backdoor. The unwitting reader thinks they are reading something frivolous but instead something important and meaningful has been snuck into their mind, which will later explode with a sudden insight, much like a meme IED.