for a sprayer, only thing that could make a large difference is the 12v diaphragm pump. everything else is tank, connectors/fittings, and hoses. the exception of hand gun/spray gun. and boom nozzles if sprayer has booms.
having a low spot for easy draining and rinsing out chemicals is a big thing for me.
i am not a large fan of many various spray guns. and will end up at various stores till i find one that is easy to tear apart and clean out any sort of clog. personally prefer a hand gun, that i can use interchangeable tips. other words, i can adjust a jet stream. or i can take nozzle end out and replace with a mister from like a boom. and have a mister spray gun. to other.
i always end up wanting more hose for the spray gun. so if hose is cheap enough i will buy say 50 feet of hose. and then get some garden hose connectors. and cut the hose up in 15 to 25 feet lengths. so i can easily undo and add extra hose length easily on the spot. having some coils of hoses wrapped up and twist tied to spray rig. makes it easier for me, due to not having to untangle the hose every time i go to use it, and only need say 12 feet max length in normal use.
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for me i prefer a larger tank, and will DIY one up. so i can redo the lowest drain port on the tank. and run a short piece of hose with a valve on it. so i can use tank like a water tank and go around and water stuff quicker by draining water out of the tank vs spraying water via spray gun. only down side, larger tanks, can be a pain in rear to clean / wash out after a chemical use. if you can get a spray tank. that has a large enough "hole" that you can stick your entire arm down into with a garden hose nozzle the better.
if i can find the hose clamps. i will go with some clamps that i can just squeeze with pliers. to loosen clamps up. vs using a nut driver or a flat head screw driver. makes for easier removing clogs.