I think you misread part of my statement, but it also boils down to preference and point of view.
I didn't mean to imply that the heritage belt was either slimmer or more formal. I meant that if the OP *already has* a slimmer, more formal belt he sometimes wears, when needed, than the heritage belt would be a nice counterpoint. I feel like the standard belt is pretty multi-purpose, however I overlooked that he was thinking about it Natural. That finish will never look right with anything besides casual/denim oriented looks. The finish on the heritage belt makes it a better candidate for a dressier belt.
And yes, neither belt is truly formal by a long shot, but everyone's needs in that area are different.