Primary considerations in piping materai selection are strength and potential corrosion, thermal effects and environmental factors. Piping materials typically used include carbon steel, stainless stee, ductile iron, FRP, HDPE, and PVC. Use of thin walled pipe requires that it be properly protected from physical damage. Blower discharge may be in excess of 200 degrees so the pipe and supports must be designed accordingly. Because of the large thermal stresses, provision for pipe expansion and contraction are necessary. Blower discharge is often insulated to protect workers from possible burns, help attenuate noise, and keep blower room temperaturs under control.
Blower droplegs are usually PVC or Stainless Steel because of corrosion concerns.
Don't see any benefit in your case for accepting carbon steel. You paid for stainless and a contractor typically will not give you full value back on a change order. Sch 10 is also acceptable for stainless steel because stainless steel will not corrode like carbon steel does. for that reason, the equivalent pipe to sch 10 stainless steel is sch 40 carbon steel.