The diamond RH-77CA is also a decent air band antenna. The Watson as described is specifically designed for air band so a good dedicated antenna choice.
Hi got both the diamond & watson performance is excellent on airband but my polar antenna which is specified for airband only is better and shorter in length.
well I live downstairs ion a condo type apt and I cant put anything outside but it sounds like the Watson would be the choice over the diamond for a dedicated airband antenna I used to own a diamond rh77 and I used it exclusively for texas dps when they were in the 150 or so range and it worked perfect never tried it on the airband but I bet it works well too
Another option is i live in an apartment too,but have a antennacraft ST 2,which runs from floor to the ceiling in a corner next to the main window and picking up Huntsville Tower from 10-12 Miles away.I use it to run 3 scanners,thru a cable tv splitter and works good on all bands,VHF,VHF High and UHF.