Sorry logged in with wrong game tag please delete.
I’ve heard of quite a few bugs in the game for both consoles. I’m experiencing one or two on the Xbox One but the 360 version also has quite a few. I would suggest reading the forums, seeing which bugs you’re likely to be able to live with the most and pick that version if you really want the game. 
I haven’t had a single issue with Forza Horizon 2 on the X1, but I never had a single issue with Forza 5 either.