The Buzzer! Had an earlier model. If having no control, barely atomizing the paint and spewing it in the general direction of the target will get the job done, this might be a good choice. (wear earplugs)
HVLP, with a bit of practice ( and there's nothing wrong with thinning , just learn to use the set up) will give very high quality results. But it is not made for covering large areas fast. Also cost many times more for a quality unit.
( I have the CS9100- nice unit-
http://www.o-geepaint.com/Sprayers/wshvlp.shtml?photo=3)
Just looked at the wagner HVLP. Not even same league. )