It's the same service on the same servers. Same servers = same content. I don't know why you guys are working yourselves up over it.
There is a different version, the newer version, which is being made for Xbox360. It is still the same service, though. Someone on Xbox1 could go to the downloadables section and see PerfectDarkZero maps, but won't be able to download it clearly becase he is on an xbox1 and is running an earlier version of xboxlive.