Better for what?

It depends on which you prefer. Like ppf. said, 'better for what?' Go with the one you like the best, that fits your budget and you think will lost best with the rest of your house.

If you want more help, post some pictures of the front of your house with links to the door so we can see what you're talking about. And explain the look you're trying to achieve. The more info you give us, the more likely you are to get helpful comments.

Walnut is not an exterior wood. Mahogany has far better weathering properties.

I have a beautiful mahogany front door and can't imagine anything better!