pcm or bitstream

In theory, neither is better. PCM means the source decodes the audio i.e. from whatever compression has been used, usually Dolby TrueHD or DTS HD Master Audio. Bitstream means the native audio is sent to the AV receiver and it's decoded there.

Most people choose to use bitstream as it lights up your amp with the format that's in use (meaning it's easier to be sure you're getting HD audio on some of the older Blu-rays which defaulted to the Dolby Digital format). Some also claim that generally the sound is better this way round, whereas others will say it can't make a difference - I've not personally done any tests to confirm or refute that.

thanks for that , ive had a bit of a mess about think the bit streams a little better , but see what you mean about the amp and its display.

That's all that matters then, what YOU think sounds better.