We went with Branch; we have “virtual” warehouses at each location (service, parts, etc.) and each of those warehouses belong to the master branch for that location.
Either method works, though--what’s important is understanding how are you going to track sales and inventory in the GL. Pretty much every area of the system is configurable where it will pull branch and subaccount from. We decided on branch because in our world, the region is the top of the hierarchy in our financials, and we went with a numeric format for branch that contains the hierarchy (branch 100 may be “South Region”, while branch 110 is “Location 1 in South Region”, and warehouse 110PARTS is the virtual parts warehouse within the 110 branch).