I`m a newbie my self but in my short experience with an AB i can and do pull the same lines with my .3 and .5 set ups . What the sizes are for is really a combination of spraying variations in viscosity of paint and volume of paint when fully depressed is normally greater with a larger needle /nozzle combination .Generally the finer the needle the finer and more intricate the work can be and the thinner your paint should be .With all my full size spray guns the system works the same except for the fact that there are more variations in air caps to aid atomisation of high solid paints and as an addition you often have a pressure feed to the paint cup that also assures a constant paint presence at the the tip .