With a 2 stage cyclone system dust collector, you get more efficiency and power than a one-stage system. The two stages mean that the dust collector will trap all the particles, big and small. The bigger particles are spun around whilst, the finer particles are passed on to the second stage for more filtration. Dust collectors with this type of technology are generally better.
A single-stage dust collector will only process dust and debris as small as 2 microns, at most. Whilst the 2 stage system in place, you can recycle much smaller particles than that. To avoid breathing problems and illnesses, you want to make sure that the dust collector can filter even the smallest particles.