I'm not saying that salvation was not possible under either of the two Gospels presented. But it still must be understood that Peter's Gospel was to the Jew and Paul's to the Gentile. Otherwise why was the difference even brought forth in the scripture? If one Gospel, it should have been addressed as the Gospel to avoid any confusion, not as the Gospel of Peter or Paul.
There is NO difference BR. Are you a KJV only person?
If not here are a few other translations that tell a different stroy.
New International Version (©1984)
On the contrary, they saw that I had been entrusted with the task of preaching the gospel to the Gentiles, just as Peter had been to the Jews.
New Living Translation (©2007)
Instead, they saw that God had given me the responsibility of preaching the gospel to the Gentiles, just as he had given Peter the responsibility of preaching to the Jews.
New American Standard Bible (©1995)
But on the contrary, seeing that I had been entrusted with the gospel to the uncircumcised, just as Peter had been to the circumcised
GOD'S WORD® Translation (©1995)
In fact, they saw that I had been entrusted with telling the Good News to people who are not circumcised as Peter had been entrusted to tell it to those who are circumcised.
Douay-Rheims Bible
But contrariwise, when they had seen that to me was committed the gospel of the uncircumcision, as to Peter was that of the circumcision.
Darby Bible Translation
but, on the contrary, seeing that the glad tidings of the uncircumcision were confided to me, even as to Peter that of the circumcision,
Weymouth New Testament
Indeed, when they saw that I was entrusted with the preaching of the Good News to the Gentiles as Peter had been with that to the Jews--
World English Bible
but to the contrary, when they saw that I had been entrusted with the Good News for the uncircumcision, even as Peter with the Good News for the circumcision
Young's Literal Translation
but, on the contrary, having seen that I have been entrusted with the good news of the uncircumcision, as Peter with that of the circumcision,