Well, lets take this into a full view
Spraypaint is great for A full body coat, but when it comes to tiny details, its hard to use unless you're good at airbrushing, and even so, you should not use Spraypaint to airbrush
Hand brush paint is different, its not good for Full body Paintjobs, you'll see the brush strokes and it'll look very messy, but yet it is good for adding tiny Details such as battle damage, Places where the Paint is scraped off, etc. So its more of a Combination of both types of Painting, which will lead you to a Sick Paint job ;-)
Depends, Spray paint like most people said is good for doing big things. but hard to do fine details, for instance the indents. so you could both spray the body, the pin stripe the indents in. either way you do it you may have to go back and forward between the two.