While i think that Christianity has a number of good moral positions it also has some pretty wretched stuff which is (at least notionally) based on what a god wants.
On the other hand, secular humanism holds as it's metric the idea of human flourishing and reduction of harm. It can encompass absolutely every moral virtue claimed by Christianity but is beholden to none of the harmful, punitive dictates that come from religious dogma.
Therefor i say that Secular humanism has the superior foundation for a system of morality.