Um, yeah there is. I dont know about all receivers, but my Yamaha RX-V2700 has a significantly different level when listening to DD/DTS through Bitstream (letting AVR decode) as opposed to PCM (letting PS3 decode and send to receiver). Overall the soundfield is noticeably better if I let the AVR do the decoding.
I switch back and forth depending on the audio track of the particular movie Im watching....but at least thats a nice feature of the PS3, you can change bitstream/PCM on the fly. My HD-A2 you have to stop the movie and go to the setup menu. Bah