Is it advisable to create a copy of a certain default odoo modules then modify it and import it as a custom module or just scaffold a module then do inheritance?

Option 1: 
copy Purchase app module folder
paste it in my custom addons folder
do some changes(required customization in the project)
then import the modified module and install

or Option 2: 
scaffold a clean module
then code it from scratch and use inheritance to get the feature of the Purchase module app