[noggin]

I hardly understand why if original content for movies is YCbCr 4:2:0 somebody will choose another color space (like RGB). I doubt that for lowcost players/TVs it can be a better choice because it will mean that YCbCr conversion in TV is worse than in mediaplayer.
For high-end equipment like Lumagen videoprocessor or highend projector it's another discussion.
A good read at http://spearsandmunsil.com/portfolio/cho...r-space-2/

Lots of media players convert from YCbCr to RGB internally - so outputting RGB rather than YCbCr avoids two further conversions (one from RGB to YCbCr in the player and another from YCbCr to RGB in the display) -so there is some sense in it.

Also SD YCbCr is different to HD YCbCr (601 and 709 have different YCbCr <-> RGB co-efficients) - and though it is possible to convert between 601 and 709 in the YCbCr domain you are still adding a conversion process into the mix - so why not convert to RGB? (In other words you can't play a YCbCr DVD (which will be 601) upconverted to HD YCbCr (which will be 709) without 601 to 709 colour space conversion of some sort...)