The site descriptions for casual and advanced mention depth and in the case of Advanced, character development and plot. 

I've received long, flowery posts with vivid descriptions and absolutely no plot movement or room for interaction.  Is that advanced?  Not so much in my book.  I like a blend of description, movement and interaction.  If you can get that to me in just a few paragraphs, sweet!   If it takes longer, fine. 

I've been in a creative writing class this semester and we are working on micro-fiction.  Trying to set a scene and tell a story in less than 300 words is such a great challenge.  Each word counts, there is no room for fluff.  And while writing fiction has different goals than RPing, I'd stack one of those tiny little fine-tuned tales I've been reading/writing up against any whopper of an advanced post any day.  

But then some people love long, lurid descriptions and don't mind extensive scene setting with lots of flashbacks and no forward motion.  Fine too, there is room for all.  After all the point of RPing is to have fun.  That is one of the things I love best about RPG, room and fun for all to be had here.