I work with both and at least for me, AMD doesn't seem being so slow.
Well, if you directly compare it through benchmark scene, you will see that even AMD's top 8core processors cannot compete with i7's that are like 5 years old.
And maru, yeah, AMD also doesn't support Embree afaik.All in all, you can still work normally with (new) AMD processors, just that it won't be as fast as Intel for the moment being.
EDIT: Removed false Embree claim, apologies. Thank you for the info Keymaster.