Most of the Subaru communities I've looked into tend to favor Subaru OEM axles over aftermarket replacement ones, despite any kind of well-covered warranty, as the hassle of a failed axle are far more annoying than paying upfront for an OEM Subaru axle.
As for the reason for powertrian warranty extension, thanks for telling us that. I'll see if I can get the same answer from my local dealerships.
"Why would I want to profess my feelings for some 3D girl?" - Tomoya Aki from the anime Saekano