I've injected with Fab, Butchers, and Kosmos and tried each with water or beef broth. Depending on the grade of beef I am cooking will help determine which I use. Fab seems to have the most potent flavor, and I have had staining issues, but can give a cheaper less marbled piece of meat some great flavor.
Staining never happened with Butchers. I would say Butchers is the most consistent with moisture and not over powering flavor.