We have a regular Controller as well as a Controller Extension. All of the logic is written in a Controller Extension, which may or may not be written in a Custom Controller.

We have a regular Controller as well as a Controller Extension. All of

1.	We have a regular Controller as well as a Controller Extension. All of the logic is written in a Controller Extension, which may or may not be written in a Custom Controller.
Answer» First and foremost, It is impossible for a CONTROLLER Extension to exist on its own. It will be applied to either a standard or a custom controller. So, keeping the end goal in mind, certain techniques, for example, must be dead in User Mode and sure in System Mode. In this CASE, using a standard controller with a custom extension is a no-brainer. Wherever the victim is, the normal Controller provides all of the Force.com platform's pre-existing options. However, after we use the normal Controller, all of the Sharing rules, as well as a user's permissions, are revered. So, if this is what we frequently require, we should ALWAYS CHOOSE this type of SOLUTION.