RVC pros: more options and filters, geoIP location, username support, several tweaks and settings, works with both Cirrus and Red5, possible to implement into existing user database/social network, speeddate and speedchat features, better sound and video quality (this will be added to CRC in a few days), in case of an error, in most cases we know the source of it and can help, better design and since it is developed for almost one year it is stable, bugs fixed.
RVC cons: while used with Cirrus (Stratus) the connection speed is slightly slower, read here why: http://www.videosoftware.pro/forum/THREAD-Red5-vs-Cirrus-Stratus?highlight=synchronization
CRC pros:: takes advantage of the latest Flash Player and offers connections via RTMFP without database. This means faster connections over Cirrus (if we used Red5 with RVC it would be the same, the enhanced speed is only with Cirrus). No filters, features, extra buttons (some users need a clean chat roulette, nothing else). Because of pure RTMFP usage less server load (affects only sites with over 20k visits/day), priority development in the near future.
CRC cons: no filters nor features yet, lower video and sound quality (the RVC source-code will be implemented soon to fix this), no Red5 yet, new software with possible bugs (the engine is based on RVC so bugs are low chance but still possible)