I have an Iwata HCS that I absolutely love, but it is the only one I have used, so cannot compare it to anything else. I will say that finally getting a dual-action was the best decision I ever made. Lots of people do far better work than I can, and do it using a single-action, but for me the dual-action is far easier to use.
From everything I have read, either the Badger or the Iwata would be a good choice.