Of course PC's are going to be better, considering that that PC might be an f'ing GTX 780 or a Titan you asswit, tell us the GPU of the PC than we can really compare, FPS/render distance aswell will play a part.
When it's PC - it is iffy. You can't label PC in general. You have to have a good PC to have good graphics. There's low quality, medium quality, high quality, and ultra high quality. I can have a PC that can only handle medium quality graphics, and a Xbox 360 could have better graphics than I do.
I use Windows Media center to stream movies off my laptop to my Xbox, + I use my internet [Xbox live] from plugging Ethernet cable into my laptop.. [As I recently moved my xbox/tv setup and no where reachable to my router. And I haven't got a wireless add on yet]