Looking to upgrade from RTL dongles for serious weak signal VHF/UHF monitoring. The Airspy, SDRplay RSP and HackRF are all in the $150-$300 range and I'm torn between the RSP1A and HackRF One.

The RSP1A has 14-bit sampling below 6Msps and appears more sensitive than the Airspy, while the HackRF can both transmit and receive. For my use case (aircraft, EmComm monitoring, some experimentation), which would provide better weak signal performance?

Current setup is a decent discone at 40ft with LMR-400. An Airspy or SDRPlay will give much better weak signal performance, especially with stronger local signals present. Budget allows for either but not both.

For weak signal VHF/UHF work, go with the RSP1A. The HackRF will not be your receiver of choice for casual monitoring - it's better for signal analysis above 2GHz. The RSP1A's superior dynamic range will serve you much better.

I own both. I have several HackRF1, various AirSpys, various RSP and can tell you the RSP1A wins hands-down for monitoring. For regular listening VHF/UHF, I prefer to use an AirSpy - the HackRF would not be my choice for that. Save the HackRF budget for a good preamp instead.

The transmit capability is nice to have but the transmit capability does not really add extra cost. That said, for your stated use case, the RSP1A's filtering and sensitivity will be more valuable than HackRF's TX capability. You can always add a HackRF later for experimentation.