I have both, find the audio on the 536 much louder & clear than the HP2. Also, we have a 700 Mhz simulcast system here, which seems to be the biggest issue w/ all the digital scanners, and I find the 536 much better at dealing w/ this type of system than the HP1 or HP2. The 536 still has audio drop off issues, but far less than my HP 2. Also the siren app for the 536 is handy, you can listen to your scanner using your Iphone or IPad & WiFi connection anywhere in your house or whatever range your local Wifi goes to. However, had some issues w/ the app staying connected when my phone switches over to cell mode, so take it for what it's worth.