IMO, the new econo-rifles have one, admittedly big, advantage over older mil-surps.
They are less expensive, for a complete sporting rifle, than for converting any mil-surp.
IMHO, the quality of econo rifles is nowhere near the quality that a good milsurp sporting conversion can be built to.
OTOH, milsurps offer the opportunity for a satisfying hobby/work, beyond just shooting - as the conversion work provides one the opportunity to either acquire or hone gunsmithing, and metal/wood working skills, to say nothing about acquiring an intimate knowledge of every single working part of the gun.
Depending upon the barrel used on the mil-surp, and the skill of the converter, any accuracy differences between an econo-rifle and a converted mil-surp would be negligible, and mostly dependent on the type of milsurp action converted - all mil-surp actions being not created equal.