Just to be clear - are you saying that Paul was given a newer "message" than what Peter preached at Pentecost or St Stephen preached before he was martyred?
And to clarify my point: The authority of the Apostles (including Paul's) was why they could command obedience. The authority was promised by Christ and first confirmed with power at Pentecost - and then by revelation to Paul, an Apostle out of season.
Authority and power was given to the Apostles. That was the first tradition i.e. - the handing down from one Person (Christ) to another - the Holy Apostles.
Absolutely I am saying this. Paul was not saved until Acts 9. How could his message be anything BUT newer than Peter's or Stephen's? Their message concerned a kingdom of believers. Paul message concerns a Body of believers. The Church the Body of Christ. Look back at the first part of Acts, before Paul was saved. Peter did NOT preach on the day of Pentecost that Christ died for our sins, was buried, and rose again the third day. Peter was preaching the Gospel of the Kingdom to Israel. Just as Christ instructed him to do.