I like this backpack sprayer because it's just easier to make up a 3 or 4 gallon load of spray and move around our hilly property with it on my back. It's much less work than carrying a 1 or 2 gallon sprayer in one hand or on one shoulder. Having the ability to fill this with 4 gallons at a time makes the job take a little less time and that's helpful too. I didn't pay attention when I ordered and I bought this piston style this time, whereas in the past we've always bought the diaphragm style. I am not sure that I perceive a real difference in use, although they look different and there are separate instructions for each in the Solo manual. This piston backpack worked fine. I am 5'8" tall and almost 70 years old and the weight and distribution were acceptable. The rod or bar that is used to pressurize the spray is at a convenient location at the side and was easy enough to pump. The spray handle itself gave me some trouble and soon became stuck in the constant-spray position because the plastic was soft and got wedged into the little groove. That isn't good, so I knocked off a star. The spray pattern is OK. I usually use fairly large drops because it seems we always have at least a little wind and I don't want the overspray going everywhere. Not a bad sprayer, although it needs a much better spray wand.