Both the HighLife and Travis Rice are stiff boards. The HighLife is stiffer though. Both are very damp rides. However, their shapes are completely different. The T.Rice is a Hybrid Rocker/Camber true twin. The rocker section is between the bindings and the camber is underfoot.
The 2011 Highlife is a two level rocker rise. The nose has a medium rise then it mellows to being nearly flat with a low rise rocker in the tail. The 2012 Highlife UL has their new All-mountain Hybrid. The medium rise rocker in the nose is still there, but now instead of being nearly flat, there is a very slight camber that goes through to the tail. I'm talking very slight camber so almost flat but not.
For icey conditions, T.Rice wins without a question. Ride Slimewalls work really well on dampening the ride on crud, but the grip isn't there like it is with MTX.
If you ride any powder, Highlife wins. The shape was built with powder in mind. I also think the Highlife is the faster board. I rode the 2011 version and that thing booked! It was a demo board as well so I doubt it had much base maintenance.
If you find MTX to be too grippy, you can easily solve that problem with an edge filer. Just go over the edges and the extreme bite will be reduced without sacrificing edge hold on ice because you'll still have all 7 contact points.
For all out carving and speed, I say HighLife. It's good enough on Ice given that you are a solid rider.
As for Never Summer... Consider the Heritage. Go hit up Snowolf's review on the Equipment Review section of this forum.
163w is a good size
Ride Highlife UL Wide2012
164 for this one
Lib Tech T. Rice Pro C2 BTX2012