I want to call addExportType() to add my custom export type to sales order grid. I can do it two ways:
Either rewrite the admin sales order grid :
Mage_Adminhtml_Block_Sales_Order_Gridand add the method call from there OR
Hook into the event - adminhtml_block_html_before and in my observer method check if the block instance I am getting is for the order grid and call addExportType() on it if it is indeed an instance of the class I am interested in.
The advantage of point 2 is that it makes the extension less vulnerable to conflicts with other over-writes of the sales order admin grid but the disadvantage is that it will be called for every admin template child block for which this event is triggered.
What would you choose and why?