I've done 4 cabinets total (3 were for family or good friends), and I've brushed 2, sprayed one and rolled one.
I started with the brush as the cabs I use are those old generic Taito's with the carriage bolts on the outside and I was worried about the bolts catching paint and then dripping. It turned out to be true that this gave me a problem, so I had to go back over the bolts with a brush to "smoothe" out the paint in those areas.
So as an experiment I sprayed one (using spray paints) and although the finish was smooth it ended up taking longer and costing more, plus I would say it didn't come out that even.
So I've learned that the roller works best for a smooth surface, brush if you have anything like the bolts I had, and lastly spray.