Buyers should prioritize pump pressure and flow rate, as these determine the efficiency of chemical application. For large-scale operations, a diaphragm pump is preferred for its durability with abrasive chemicals. Ensure the tank capacity (ranging from 16L for backpacks to 1000L+ for tractor-mounted units) aligns with your field size to minimize refill downtime. Additionally, look for adjustable nozzles (fan, cone, or stream) made of ceramic or stainless steel to ensure precision and wear resistance.