Here are the two compressor maps.
ys-trim:
http://www.vortechsuperchargers.com/...-trim_map.html
s & t-trim:
http://www.vortechsuperchargers.com/...-trim_map.html
First the impeller speed has to be calculated. It can be done here: http://www.vortechsuperchargers.com/...pspeedv-1.html
At 12lbs of boost the S-trim is more efficient than the ys-trim.