Many years since l flew the beast. The mob l worked for had nothing but -41's, except on the contract aircraft l was on with the -42's
If l remember what the engineers said, it was the ability to operate with hotter temps. This was accommodated by the single-chrystal turbine blades. l guess that means the -41 had multi-chrystal blades. But otherwise the motors were much the same.
We also had the hydraulic under-carriage which was a nice touch too.
halas