The oXbox BC on the 360 was a good idea, but it was never really implemented that great, and a lot of really good games never made the cut.
I can't speak to how the XB1 will handly oXbox emulation but I'd be pretty confidant that a lot of titles won't make the cut there either no matter how well it is (or isn't) done.
If you can find an Xbox, especially one modded with a mod chip (or if you can find and install a mod chip yourself), it's well worth picking one up.
I tossed a nice big HDD in mine and ripped all my games to it's drive. There's some really good games on the system, and it can output native 720p so it tends to work with a competent upscaler pretty well.
A bit off topic from the 360, but if you have an interest in the system, it's pretty damned cheap to pick up. It also makes a pretty rock solid emulator platform as well if you care and don't already have something else already doing that.

