Usually we need to add to the Order Grid some column, so let take this as example.
There are 3 ways to do that:
- Rewrite the grid block in our custom module
- Use an observer on the event
- Use a Layout update
(let don't consider the alteration of the collection to make things more easy)
- First method is the most powerful but It leads to conflict in the scenarios.
- Second method is in IMHO resource consuming as we are adding an extra code step for every block we are going to render
- Third step is a layout update so should be the most advisable ... but are we sure it will work always ?
Other consideration are welcome
Method 1: - http://inchoo.net/ecommerce/magento/programming-magento/adding-customer-group-column-to-sales-grid-in-magento/
Method 2: - http://www.atwix.com/magento/add-column-to-customers-grid-alternative-way/
Method 3: - http://www.atwix.com/magento/column-to-orders-grid/