In my opinion:
Budger: although there are many shops selling this stuff is in Europe this brand is from USA and this reflect in the price;
Isumiya: i do not know;
Iwata: is the Ferrari of the airbrush like a Ferrari you need "roads" for put this machine run, we need even a top airbrush for the service that we do or have cheaper alternatives ?
I've been tempted to buy one but for vanity not for necessity...;
Paasche: the same of Budger;
Harder & Steenbeck: a european brand that you can found spare parts easily and at attractive price, i have a Evolution since 2006 and i don't want other...very precise. Before this i had an Aztec (American brand) that the only advantage was at the time of cleaning, which was only necessary to replace the nozzle of the airbrush where he had the needle but it was not as precise as this;
MIG: never painted with any of these but I think that is one of those airbrush type "Chinese" to put the name of a renowned brand to "tell" that is good and charge a high price for the equipment.