Gravity fed and suction fed spray guns.
Moderator: martauto
the suction requires more air pressure and is heavier when fully loaded. you will notice how much heavier when you get half way round the car. most if not all profesionals now use gravity as they are much easier on the wrist 
also there is no paint waste in the cup and they are much more manouverable around arches and sills plus no paint pot on the bottom to scrape along the roof. They will both need refilling part way round. tip size is also a factor depending on what paint you are spraying, primers need a large tip approx 1.8mm, 2k solids and laquer need a smaller tip 1.3mm - 1.4mm and base coat need a smaller tip ideally 1.2 mm. I use a devilbiss gun but these are expensive there are lots of cheaper guns but always buy the best you can afford.
also there is no paint waste in the cup and they are much more manouverable around arches and sills plus no paint pot on the bottom to scrape along the roof. They will both need refilling part way round. tip size is also a factor depending on what paint you are spraying, primers need a large tip approx 1.8mm, 2k solids and laquer need a smaller tip 1.3mm - 1.4mm and base coat need a smaller tip ideally 1.2 mm. I use a devilbiss gun but these are expensive there are lots of cheaper guns but always buy the best you can afford.