I know that Larry is very happy with the air diaphragm pump since he switched from the 12 volt pumps.
It was a lot more expensive to make the change over but when you do roofs all the time like the guys in Florida do, sometimes you need something stronger and that will last longer in the hot, humid climate along with the chemicals being used.
There are many guys that made the change over to those kind of pumps but typically those are guys that do a lot of roofs, if you don't do a lot of roofs then the other pumps will probably take care of you until you get to the level of many roofs per week.
When My Bandit goes out, I will be going to the air diaphragm pump also, I have seen it in use and seen what it can do.
The pump Larry has can do up to 8gpm but you really do not need that much flow on a roof........unless you split the flow and run 2 guns/wands off it for the very large roofs, with that setup he has, all he needs is another gun/wand and some more hose and he is good to go for the larger roofs.