12.1.2.7 Released - Update or Re-image?

Now that 12.1.2.7 is released we are seeing multiple installations asking questions on their update/upgrade path.

.

For example, we received a SR where the user with an  ODA was asking for recommendations upgrading from 2.1.0.0.0   -- !!! (The first ODA version from 2011)

- The recommendation was fairly simple:

   Backup your databases, reimage to the highest acceptable version:

I would like to use this thread to discuss pros and cons of Upgrade vs. Re-image which can also provide general questions you have had to address when preparing to get to a higher ODA level.

ODA Users: Please add some comments or experiences on how,what and why your chose your update method fitting your business needs.