They are probably different for different people because the lasts for different boots are made to fit different feet. One company might have several last shapes they make different models off of. I found, for instance, that some models of Danner boots fit me very well while others did not. The folks at Danner explained that the shape of the last they made the boots I liked from was the same for those models that fit me best. Other boots the did not fit well were off different lasts.
I like Merrell Ventilators. I used to wear Danner or Alico traditional leather hiking boots. Now I wear lightweight hikers. Saving a pound off the end of your leg will make those hills easier to climb; especially at the end of a long season of digging gobblers out of those hills.