Who's running low 10s with leaf springs?
Biggest thing about the SS Springs, regardless of any other "gizmos," that you won't get with other type leafs (XHD's mono, whatever) is reduced body roll under launch torque. That was their design goal, works great and helps the car launch straight.
Many are running very fast w/SS Springs. Proven record. All esle is just academic arguing points that can be proven right or wrong either way.
SS Springs still best bang for the buck, hands down, IMHO.