I've got a walnut/maple end grain and it doesn't matter which one you get, your knives will leave marks. It was heartbreaking for me at first because it's so pretty but after awhile it just blends into the board and adds character.
Depends on the type of Maple or Walnut, there are many types of each. A hard maple will have a specific gravity in the low 7s while a maple is typically around 5.5 to 6. But there are softer maples that drop down the the mid 5s also. SG at 12% MC.