Its a quirky industry where we tend to defend what we do rather than take another's experience and think that they are actually doing something better than our self.
I got tired of my Omni pump leaking so I rigged it up a different way, hated the battery always dying on me 1/2 way through so I installed a bigger battery, found the battery/pumpup sprayer wasn't putting down enough prespray or I'd need to carry a 5gal jug around so I switched to a HF.
A lot, if not everything, depends on your cleaning style, what you find works with your method. Some guys like cleaning room by room, I prefer prepping multiple rooms then cleaning them,
also depends if you work alone or in a team. With a team, a battery sprayer may work better where one guy is prepping a room ahead of the guy cleaning and then there is no need to share the pressure line or run a 2nd line.