I've only used the Beersmith app, and switched to brewfather last year. I vastly prefer Brewfather. Beersmith didn't seem very intuitive to me and always seemed a little clunky. I like how Brewfather has recipes and a batch recipe, in case you need to make last minute adjustments. The water section seems to work well is the best non-bru n water tool I've used. It seems like Brewfather is updated more frequently than Beersmith, adding malts, additional funcitonality, etc.
mIBU looks pretty nifty, I might have to check that out.