allio:
The Shield has a lot more grunt than a basic Chromecast so it's quite likely it has much better performance in mirroring mode. But the quality will still never be able to match direct streaming.
I'm sure that is true but it is useful to define terms when making a statement like that. In our case, there is no discernible difference. We have an older Sony TV, 50 inch, 1080p only. Our broadband is wireless RBI, so we can't stream 4k or anything like that and we couldn't watch it in any case. Much of what we do watch is only SD so in terms of video quality, there is no difference. Buffering, dropped frames and stuttering would certainly make a difference, but we haven't had those kinds of problems so we can't perceive any difference. I have a sense that OP is not concerned with HT quality, just getting a watchable picture to the TV. For that I think screen mirroring would probably be adequate unless trying to render from something that couldn't handle the load. I don't know for certain but sometimes a degree of purism creeps into these kinds of discussions and they become about the 'correct' way of doing something instead of the way that merely works well enough.