Ride large for less. The 27tpi version of the Surly Endomorph has all of the go anywhere, big volume features of the 120tpi tire but with a little extra weight behind it.
These shoes need some wide feet, While it may seem like a great idea the Surly Endomorph won't fit your standard XC or DH rim. It needs a rim width of at least 65mm (more than twice the width of an Alex Supra D or almost three times the width of a Mavic XM717). The Surly Large Marge or Rolling Darryl are your best bets for rim choice.
The center portion of the Endomorph''s tread is comprised of widely spaced chevrons made up of small, low-profile knobs. Higher-profile knobs, at the outer edges of the tread, provide cornering traction and lateral stability in the loose stuff. No tread pattern is going to be perfect in every condition, but the Endomorph''s tread tends to perform quite well on a variety of surfaces. Truthfully, the casing volume has as much to do with the tire''s performance as the tread pattern does.
High volume allows the use of low pressure without much risk of pinch flats. The use of low pressure allows the tire casing to spread out on the ground, providing greater traction and floatation due to the increased footprint. The tires can be run as low as 5 psi in deep snow, but 8-10 psi is generally low enough for most snow and sand riding. Want to ride on harder surfaces? Pump ''em up to 15 psi, if the surface is hard, but rough up to 28 psi, if you''re riding pavement or smooth, hard dirt. Of course, this is just a guideline. Trial and error/success is the best way to determine what pressure will best compliment your riding style, trail (or lack thereof) conditions and your weight.