From practical experience, they are just 2 different IOS.Depends on your luck whether you will have better or worse quality of life between the 2 OSes.That's a compromized way to say about them.  My actual experience is worse with IOS-XR.

I've got some useful information from this thread, so I think it will be also useful to share my information in contribution to this.I happen to get involve in some network that have > 300 switches with diameter of around 20 switch hops. It is relati...