I agree. I don't see it being possible to always handle like a 121".
For example, take the situation where snow conditions are hard enough that under moderate acceleration the rearmost lugs sink all the way into the trail yet the front of the track hasn't fully penetrated. With the XTX in these conditions lugs all the way to the back of the track will actually still be in contact with the snow.
Another situation to consider is where the trail is moguled and some of the time while cornering it is only the front and rear of the track (+ the skis) that are touching the ground.
Essentially at least under certain conditions, steering while accelerating is definitely going to be more like a 144" than a 121".
I still think this is going to make a great crossover sled that will most certainly be the best 4-stroke off-trail/crossover while still handling well on-trail.
I know one group of riders that this would make an excellent sled for. They spend at least 75% of their time riding ungroomed, deep snow Quebec trails. For them in the past Yamaha simply didn't make a sled that was even an option for them. This one is not only an option, but it is probably an ideal option (once the larger aftermarket gas tank and tour buddy are installed and most likely the shocks re-valved...).
For 100% trail riding, while it still might make a good sled for some, I'm convinced there will be some compromises.