What is the best off duty handgun?

The one you have when you need it. This is a personal question answered by a few questions.....

1. What do you have?

2. What do you wear?

3. What are you comfortable with?

4. What are the expectations of your department?

There are others, but you get the picture. The first rule of a gunfight is to bring a gun. Some prefer full size autos, basically because you are never off duty, while others prefer small caliber weapons...just in case.

It is entirely your choice. The best one is the one you have.