Tubeless fatbike setup, does valve choice matter? I've got a pugsly setup as tubeless, running endomorph tires, typically I run between 8 and 12 PSI in the tires depending on the conditions. 

Is there a significant difference between performance of presta vs schrader valves at these low pressures?
As far as I'm aware, at these pressures, there'll be no difference in performance.

A bigger issue might be the rim. The value hole will be either Shrader or Presta sized and will either not fit a Shrader or be hard work to seal with a Presta.