I'd start with the intended application and then compare the practical specifications. For portable equipment, I would look at the supported bands, scanning speed, alert system, battery runtime, environmental protection, and how much information appears on the display. The Zaruba A3 is one example worth examining: its published specifications include simultaneous monitoring of three frequency bands, a 3.5-inch display, and a stated battery runtime of 6–8 hours. You can review the details here: https://zaruba-store.com/products/portable-passive-rf-monitoring-devic I'd also pay attention to the stated limitations rather than treating the maximum detection range as guaranteed in every environment.