Christianity and Buddhism (as well as many other religions) agree on a lot of the things you should do, but not why you should do them. Christianity says everyone is made in the image of God, so should be treated with love, while Buddhism (as far as I know) says showing compassion improves your karma and brings you closer to enlightenment. It might not seem like that difference matters, and according to some religions it doesn't, but some religions (especially Christianity) that difference in reason means everything. With Christianity, the only way to heaven is through Jesus, so a Buddhist living a life of love and compassion would be no closer to heaven.