Like ICM said, it is all about balancing act of several things.  I have better going building a scene rendering regular and no AA. I prefer document size 810X607 initially.  Other peeps like different sizes initally.  As the scene develops I may change to regular with AA turned on and plop render in bits.  When it all comes together I may go to superfine and plop render a few sample areas to see if the higher setting is worth the longer wait.  Finally I increase document size and do my final render.   

One quirky thing I didn't discover early on with B5 was that saving the rendered image as jpeg created terrrible aritifacts.  I save image as .tiff now and convert to jpeg in post work. 

B6 has different jpeg settings but I haven't explored them.  I'm happy saving .tiff.  I played with fine art setting once or twice but my aging eyes couldn't see a difference.