Cuben doesn't absorb water like silnylon so you save ounces when you pack up a wet tarp because you can shake nearly all the moisture off a cuben tarp.
Cuben doesn't stretch so you save weight on tensioners (my est .6 oz per)
Cuben softens with use and gets quieter.
A HG 4S cuben at 6.5 oz compared to your 10x10 silnylon at 12 oz is a 46% savings.
I've seen no adverse effects from cold weather on cuben and I camp quite a bit in sub 15* weather. What is your source on it becoming brittle when cold?
Is it worth the cost, only you can say. In the end if you like silnylon, then that is what you should use.