When using melted butter, is rendering (clarifying) always preferable?
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.