Both have the ability & potential, both also better on the ball than Pratt, Litherland is a year further along than Atcheson in terms of age & experience though.
Edit - I do not think that either will feature regularly for the first team this season (barring an injury crisis in December/early January).
I can see O'Riordan being recalled as cover for Miller on the right of the back 3, Pratt being cover for McLoughlin on the left, and an older head being brought in to cover/challenge Wharton in the middle on a short term or loan deal (discounting Carter this season based on his injures)