How was Paul's apostleship different from that of the twelve?
Paul's apostleship was entirely separate from the twelve. The twelve were apostles of Israel, chosen within Israel's borders. Paul was commissioned as the Apostle of the Gentiles on Gentile ground. He was both Jew and Roman citizen, so he could not have fulfilled the qualifications Peter set for Judas's replacement.
Les teaches that Paul had absolutely no connection whatsoever with the twelve. The twelve were Apostles of Israel, chosen within the borders of Israel. Paul, by contrast, was appointed the Apostle of the Gentiles and was chosen and commissioned by God on Gentile ground. God selected a man who was not only a Jew but also a Gentile by citizenship—a Roman. When Peter in Acts chapter 1 laid out the qualifications for the man to take Judas's place, Saul of Tarsus would never have filled that requirement. Les notes that some theologians thought Peter was remiss for letting Matthias take Judas's place instead of waiting for Paul, but that would never have worked; Paul would never have fit. Paul separates himself from the twelve.