Why be good?

[Esquilax]

Santa is more believable?

Yes, of course Santa is more believable: the Santa claim relies on less magic than the god claim, and requires one to accept fewer unproved premises on faith. It's more reasonable to believe in a being that can do some supernatural things on faith, than it is to believe in a being that can do everything, on faith. If we're talking about what's more reasonable to believe... Santa wins.

Grown-ups know that they are Santa. Kids who are older know that their parents are Santa. Parents eventually tell their kids that they were Santa. If you go to the North Pole, can you find Santa's workshop? Can NORAD track Santa's sleigh every Christmas eve?

No?

How does this work with Christianity?

The beliefs are largely the same, in terms of evidentiary support. The only real difference is that, where parents own up and admit that Santa isn't real when their kids start questioning, there is a large and committed apparatus in place to keep people believing in god, in the church. There's whole segments of community extolling the virtues of taking this god claim on faith and never questioning it. Parent's don't just admit that they have no reason to believe in god, and they back that up with horrible threats of hell. That's the difference.

And can you find evidence of god? Can Norad track god?

No?

Then why the hell are you asking these questions as though there's some significant deviation in the level of evidence available for either claim?