I don't see the differences in the baptism accounts as signficant at all. In each account God the Father speaks from heaven identifying Jesus as his beloved Son and saying that He is well pleased with him. Were the statements made primarily TO Jesus with the crowd hearing them or primarily to the crowd with Jesus hearing them? I don't think that matters at all. What matters is what was being conveyed both to Jesus and to the crowd about the Father's opinion of Jesus. In that respect, the accounts are in total accord.
The Greek language of the day did not have quotation marks. The narrative genre in which the gospels were written did not require the authors to try to repeat statements word for word as if they were court reporters taking down testimony. The standard was to report accurately what was being conveyed.
There's no contradiction in what God conveyed. One writer doesn't report, for example, that God made this statement about John the Baptist while another says he was speaking about Jesus. Likewise, one writer doesn't report the Father as saying that Jesus is His beloved son in whom He is well pleased while another claims that He said that He disapproves of Jesus' performance in some regard. Those would be genuine contradictions.
To give a modern example of similar insignificant differences in reporting, one reporter might say, "President Reagan today demanded that Mikhail Gorbachev demolish the Berlin Wall." A second might say, "President Reagan exhorted Secretary General Gorbachev to remove the wall." A third might say, "The crowd roared when Reagan exclaimed that Gorbachev should tear down the Berlin wall." A fourth might say, "Standing at the Brandenburg gate, Ronald Reagan exclaimed, 'Mr. Gorbachev, tear down this wall!'"
There are a number of differences in those four accounts. Are any of the reports inconsistent regarding what really happened? Reading them, would you say, "The reporters' accounts are hopelessly contradictory. They can't agree on exactly who said what or whether he was really addressing the crowd or Gorbachev. The whole thing shakes my faith in the accuracy of reporters. If I can't trust them in this, I'm no longer going to believe a thing they say"?