just use "PS3 Media Server" it will stream any media file type you throw at it. Choose a video folder and choose a music folder and the PS3 will stream from your Mac/PC. This is way way way better than using Airplay anyway since it supports just about every media type.
That's fine if you keep all your media together, but Airplay supports pushing streams from devices dynamically.
IMHO Airplay was never intended to be a DLNA replacement. (although it can be )
It was designed for an Apple centric environment such that when surfing on an iPad and you find something on YouTube for example and want to share it with family, just send it to Airplay device.
Using DLNA, save video, copy to DLNA server, then select on DLNA client.
DLNA's great for static content like your movie library, but Airplay is better for random dynamic content.
The bottom line is they are complementary, not exclusive.
I use both. iTunes homesharing and Airplay for Mac and iOS devices and the same library shared using Playback (DLNA server) for Windows PCs and my PS3.