Tom A. wrote:
Knobbies are really a bit over-rated for off-road use if you have tires that can conform to the surface anyway...How much mountain bike experience do you have? On what type of terrain?
Your above comment may apply to dry straight line traction, but once you lean the bike in to a turn, introduce mud/moisture, or during aggressive braking, you need knobs.
If you climb a grassy wet hill, ride on loose pine needles, or a multitude of other surfaces common in east coast single track, the knobs are essential. You need to dig down, or dig in, to get traction. Surface conformity is insufficient. I say this after a few hundred hours of recent experience playing around with a 27.5+ bike (27.5x3") while running pressure from 10-20 psi.