Four things.
1. More of Paul’s letters survived, so more of his views and sayings survive, making him more influential in history.
2. Without Peter, there would be no Paul or work for Paul to do, so Peter is still the foundation.
3. Although they did not always get along, there is no evidence that they were opposed to one another. They disagreed on a couple of things. That is it. For the most part, however, when you read their writings in the Bible, the message is more or less the same.
4. Paul’s past is irrelevant. Don’t forget that Peter denied Christ three times and let him die. What’s the difference? The whole point of Christianity and Christ’s message is redemption and forgiveness, so their pasts don’t matter. It is the message that matters.