Yeah, a stiffer board will be better for carving, but more noticeably when riding choppy snow. A stiffer board will be more stable, powerful, responsive, and more dampened. A softer board, however, will be just fine at lower-medium speeds and on hardpack and groomers you shouldn't have any problem. Ice is a larger issue, and many boards will have trouble maintaining an edge. Overall, stiffer= better all mountain and therefor better carving and stability on variable terrain.
I might also add that I am 140 pounds and the board I rode last year was a size 137 forum youngblood that I got in '07 (when I weighed 40 pounds less and was 6" shorter). I bombed hills as often and as fast as I wanted, and while I took the very occasional fall due to loss of grip on ice (I ride in southern PA where the ice gets REALLY bad) or just loss of control on choppy snow, I was usually fine and very rarely had any issues. I had to work a little harder, but I could ride all around just fine. So I think that something like the Disaster really should be fine for charging around, and any board for that matter should be at least ridable (unless you are doing back country cliff drops, which I wasn't on my 137 forum).