Audio Encoding question

[BeardedNinjaGuy]

Since updating my HTS ive been going through and listening to every audio variation I can get just for kicks.

Ive been wondering, if there is a "Ranking" as to what types are better than the others when multiple options are available on some discs. IE DD, DTS EX, Dolby EX ect, Obviously a 6.1 would be chosen over a 5.1, but sometimes its not so clearly labled.

Is there a resource about that ranks the audio encoding qualitys in a better or worse type category? I realise that some are entirely up to the job the studio did in making the acutal tranlation, but when given multiple choices on the same disc, im curious as to what one "should" be the better choice.