2ch pcm or dolby/dts 5.1

[stow123]

I havent got an up to date reciever so can only use optical so would it be best to listen to 2 channel pcm or a surround track in dts and dolby.I think the ps3 can play a 1.5mps dts track using a reciever with optical is there much difference between dts on a dvd player about 700kbs and 1.5mbs.Also even if you arnt using hdmi and just listening in the basic way and still only getting 1.5mps from it does a HD dts track sound better than a normal dts track even if youre still listening at the same bit rate.