Well, ...... I couldn't agree with you more, Horsemany!
I've been studying this topic for several years, now; and there are, indeed, many variable in either manufacturing process that affect ultimate barrel accuracy.
A hammer-forged barrel is as likely to be adversely affected by: machine wear, sloppy setup, or a continually eroding mandrel a as cut rifled barrel can be by either: misalignment, chatter, operator error, or a dull button on a barrel cutting jig.
Mandrel formed polygonal barrels do tend to seal the bullet more tightly as it moves down the barrel. This is because of the shallower, 'hills and valleys' formed by the polygonal rifling. Still, I personally do not think a particular type of rifling has any greater or lesser effect on barrel accuracy.
(You need to remember that Hart or Schillen barrels are button cut and every bit as accurate as any barrel can ever get!)
What does significantly effect barrel accuracy, especially on longer barrels, is the taper that's applied to either one side of the bore or the other: From inside the barrel this means a larger ID at the chamber, and a smaller ID at the muzzle.
From the outside of the barrel this - usually, but not always - means a gradual taper in the outside OD from the chamber to the bore. All of these different rifling methods use their own particular technique in order to accomplish this. Cold hammer-forging equipment is the most expensive machinery a barrel manufacturer can employ; but, the cost and time for each barrel that is produced is much lower than either of the other conventional methods. (broach, and button forming)
As to whether or not hammer forged (polygonal rifled) barrels are more accurate? They may, or may not be; it all depends on (1) the condition of the shaping mandrel, and (Ready?) who made the barrel. Will a cold forged barrel produce more velocity by sealing the bullet better as it travels down the bore? I'm going to say, 'Yes', but only slightly, and this is because, with other things equal, the ultimate limiting factor is always going to be barrel friction.