The Christian bible makes no qualms about slavery. It condones it at every twist and turn, even condoning returning runaway slaves to their brutal masters. But the Quran is a little less certain about the morality of slavery.
In Surat Al-Baqarah verse 2:178, Allah appears to condone slavery, at least in regards to how legal code is interpreted. The Quran makes no attempts to condemn slavery in this passage, which is in keeping with the other branches of Abrahamic religion.
But if one skims backwards one verse, they would find that the Quran explicitly calls people who free slaves righteous.
At least in the case of that verse, the Quran exhibits more morality than the bible.