Replay Radio 9 offers a new audio recording technology. It can capture streams (like Sirius/XM) that Replay AV can not. Additionally, while these streams are captured via audio capture - none of your PC sounds are captured - AND you can capture multiple streams simultaneously.
Replay Radio 9 offers an up-to-date, robust media guide with thousands of listings of radio stations/shows/podcasts. Replay AV's media guide is not current and some of those links may not work.