I have no firm information but from what I see the skis have not changed much. I skis the Head, so I am obviously liking that ski more, but here is my 0.02:
First, a disclaimer- if you can find a demo, take them out side by side, that's the best way to decide.
Now, I think it depends a lot on how you ski. Both of these skis will be a great midfat all-mountain ski (the proverbial one-ski-quiver). They are rather different though, I call the Heads the "un-Mantra". Basically Mantra is a stiff ski with the tail stiffer than the front. Whatever it is, it is not a damp ski. It likes being driven hard, and I think it relies on stiffness to manage the off-trail terrain. Heads are medium stiffness with a quite a lot of damping, so they rely on that damping to tame the crud and everything else in between. The feeling is almost like having a good suspension on the ski- you can feel the irregularities, but the feel is muted, so you just flow through the chopped snow. Both skis are not wimpy, so I would not be concerned about lack of top end. Mantra will be a better hard snow ski, Heads are definitely a better soft snow ski. If you like to be a hero on every turn, Mantra will be more to your liking, if you like to go everywhere, and want the ski that adapts well, the Heads wont disappoint. One final word- if you get the Heads- immediately re-tune them to 3/1 (side/base), that makes a huge difference.