well accuracy will be about the same generally
then you have velocity which will differ some but in .308 the velocity increace shoudlnt be too huge
arguemnt in favor of the 20" barrel-
more accurate at short range (shorter barrels tend to be slightly stiffer), more managable
arguemnt in favor of the 26" barrel-
more accurate at long range from faster velocities
it all depends what you want, a precision rifle for longer ranges, the 26" barrel is the way to go, you want a smaller more managable rifle the 20" Savage is the way to go
Remington offers the same kind of thing, the 700P and the 700 LTR