If by featherweight you mean exclusively 126 pounders, I could see Sanchez, particularly if Azumah Nelson is probably more of a junior light than feather in terms of his peak abilities and best wins. If we throw in 130, where Alexis Arguello was at his best, I would give the nod to Alexis, however.
If it isn't already annoying (in my view) that we've had the so-called junior weight classes, add in that super bantamweight and junior featherweight are the same thing. I think it could have cleared up a lot of the muddle if boxing had just stuck with fly, bantam, feather, light, etc.