Cookie,
Checking out the Wood Database,
walnut is in between
cherry and
maple in hardness and weight, so is probably the better choice, just using these specs to choose. Another spec that is probably useful in choosing a wood for boards is crushing strength, and it is also in between there.
As for any of these hardwoods in cutting boards, this is where cheap is often just that, as there are many maples out there, and the woods can be cut in ways which will guarantee their warping. So the money spent on a Boos will be well spent.
Fuzzy,
I am surprised that you cold find a chopping board made of alder! It is softer than many varieties of pine, and is often suggested for people starting out hand carving, due to it's softness.