I am not sure what you are asking but there are huge things the Xbox cannot do. No AirPlay, no iTunes media playing, no iCloud music streaming, no photo stream and the atv is quieter, uses less power and takes up less space.
That is not to say the Xbox is a bad media device it is fine I used before the atv. But if you have ios devices, iCloud, iTunes match and iTunes purchased content to me a jailbroken is everything the Xbox is and more.
What pissed me off about the Xbox and MS in general was the need to join Xbox live to get Hulu, Netflix and MLB apps on top of the cost of streaming. Utter bs IMHO and that was the end of Xbox being my media center.