I work for a shop that sells both. When it came down to it, I went for the Anthem X because the weight is nigh on identical, but the Anthem is a touch lighter, and to me felt like a faster, more efficient bike. It's also a stunning descender. Also, the front end was 1cm lower on the Anthem which was important to me- I run my front end as low as I can get away with.
To me, the Anthem was more nimble and more fun going down as well as being a better climber. I'd disagree with the comments about it not being a good descender above- it's massively capable. To the point where I keep thinking about firing on 120mm Sids and using it as my only trail centre bike.
Also, and this wasn't a small factor, it was much better value.
I'd been dead set on a Fuel until I played on both and the Anthem won. And, if it makes any difference, my boss chose the Anthem over the Fuel too.
None of this is to say that the Fuel isn't a good bike, it is. Definitely worth having a play.