Here is my take on it.
History:
I rode a Pro from 2011-2014. Loved it, great sled, got tired of the terrible resale and instead of dumping money into my 13 pro to put a 3" track on it, I decided to give the T3 163 a try.
This is where it might change things a bit. Where I had so much fun on the pro and liked a lot of how it felt and I knew what I didn't like about the doo I immediately made changes to the t3. It got a post forward kit, dan adams bars, gripper skis, fox 3 evol R's up front, Toms emtion skid, tki belt drive and diamond s can.
I jumped on the sled and immediately loved it. There was now getting used to it. I was immediately comfortable. The issues of washing out that others had I didn't. The tendency to wheelie was easily fixed with some adjustments to the skid / air pressures. I really have very little if any complaints on it.
In January last year, I got to be one of the demo riders on the Axys. I didn't end up on their little promo video because I was one of the only riders to criticize it. Without getting too long winded. Here is what I found. Snow conditions were pretty bad. Mostly set up and very difficult to find and steep and deep. I loved the power and snappiness of the new motor. Hopefully those lightweight cranks hold up. If they do, it will be awesome. We did find some steep and deep powder for a couple short tree runs. It rallies in the trees. Handles well, initiates corners well and climbs well and gets up on top of the snow rather quickly. Noticeably better than the pro. My chief complaint was that in the set up snow it felt like the old xp and wanted to fall back downhill. Since the snow conditions were mostly set up, my experience was 90% set up snow fighting the machine (I think mostly due to the elevated center of gravity) and 10% steep and deep where it really shines. We did move the skis out of the narrowest position and it felt much better on the set up snow. Overall I liked the axys and feel that for advanced, aggressive riders it will really shine. I just worry that some of the newer riders may struggle, specifically on typical set up days. I know most of us here buy a sled for how it performs in the deep, but unfortunately a lot of rides are still set up / not perfect snow.
As for side by side comparisons, I have yet to do that. Fortunately I have a few Axys in my fleet this year and I should get lots of opportunity to ride both side by side. I am anxious to get more seat time on the axys and get a better feel for it. But as for now I have zero regrets with sticking with my t3 for another season. Not to mention I wasn't anxious to be another polaris guinea pig.
There's my 2 cents.
Upgraded shocks and skid geometry--let the games begin 
