Neither? The stair will be too soft for 10% park. From CAPiTA look at the Quiver Killer and BSOD. The TWC is a pretty basic board. I think better can be had for the money. Drop the extra $100 and get the Flow Infinite I-Rock. Or get a last years something.
That thing I do to escape the world and have fun with my friends
I ride the 156 Scaremaster which is an exact replica of the stairmaster and its softer than an all mtn board but not so soft that it can't ride all mtn. But obviously you should buy a board more suited to your style of riding.
I found the darkstar a little too soft for all mtn...but I'm also about 190lbs. If you're on the lower end of the weight spectrum it would probably be a pretty good board esp if you want to venture into the park now and then.
are you interested in the stairmaster because it's cheap?
Because I bought it for that exact reason. The board is great if you are riding park, a few jumps but mostly rails. If you are doing 90 percent all mountain I would highly suggest no. I love my stairmaster for what its designed for but I say a big no for what your doing.
I chase powder for a living. As long as I can get that tingly sensation and some white stuff in my face every day, I will be perfectly content with life.