While both meters contain the same hardware the key difference in selection is the location and accessibility of the plumbing as well as the stage of development. If you are building a new development then a Wall meter would be a better option especially if you can specify the plumbing.
What is the purpose of a water meter? To measure the amount of water delivered to a household. A water meters main function is to register the amount of water consumed by a customer so that an accurate bill can be charged.