Recently a student and I had this discussion as we were working on a painting of a field of flowers...
She said," I was thinking about the different styles in class, and I remember looking at the realistic one, and thinking it's very good, but something is missing. I love your work, right or wrong, I call it impressionism. And I realized the difference between your painting and the realistic one was the suggestion of movement. When I look at your painting I can almost feel the gentle breeze making the flowers bob, I don't get that in the realism. Am I onto something?? "

Yes, I think she is on to something.  So many artists struggle to loosen up their paintings and show their passion or "impression" of a moment in time...so I thought, why not start out loose to begin with...and bring it tighter and tighter as you progress, with the option of pushing it as far as you want....or  not! 
You can't loosen up an already tight painting.  And in fact I think that unless you are an expert drawer, which most of us are NOT, then any little mistake in the drawing sticks out very loudly and looks far more amateurish than a suggestion would.  So many more realistic paintings look "stuck"  and at times even painfully so, unless the artist really knows what he's doing.  

Still, I try really hard to respect the personal style of each artist, because even though I paint the way I do, meaning more impressionistic, it does not mean it is the only way.