Through their first two minor league seasons. It's important to note that Hellickson spent about a day in rookie ball, where as about a third of Barnese's time has come in rookie ball. As impressive as Barnese's numbers are when compared to contemporary performances he's not quite as strikeout heavy or walk preventive as younger Hellickson. He does seem to suppress homeruns better though.
Fun fact: in Vero Beach this season, Hellickson had more games started than walks and homeruns allowed combined.