Essentially clarified butter is butter that has all it's water and milk solids removed. All that is left is butterfat.
Pros and Cons of Clarified/Rendered butter:
Pros:
- It can be stored longer than regular butter
- It has a higher smoke point so can be heated higher without burning
- Does contain negligible lactose for those lactose-intolerant
Cons:
- Effort. It requires so time to melt the butter, boil off the water, filter out the milk fat, and resolidify the butter again.
- Taste. Because the milk solids are filtered out, it has a milder "butter" taste than unclarified butter. Of course it will still be much more rich and buttery compared to regular vegetable oil.
With this information in mind, I will leave it to yourself to decide when you should and should not use clarified butter.