Well I'm thinking now in terms of HD quality (assuming no multiplexing, which they love to do) in majority of COFDM countries with 7 or 8 MHz channels. And comparing DVB-T vs 6mhz ATSC in terms of ratio of assigned resolution of Y/C - and if it still reflects the old theory that "Chroma res doesn't matter that much" - whereas we see
picture simulations of progressively higher C res and, what do you know, it does matter!
So, it seems to turn out Y/C quality is more a function of
sampling formats than given availability of luxurious broadcast bandwidth (DVB-T 8mhz channel)? - was curious about this. And some mastering formats have Y=C!!
The upshot of this being that the philosophy of desired chroma res has evolved from as low as one-fifth luminance to as high as full luminance res!