Optimization due to constructor initializer list

Question

Constructors should initialize all its member objects through initializer list if possible. It is more efficient than building the constructors via assign

Answer 1

Because it initialises directly, instead of default initialising and then assigning. It likely won't matter performance-wise for PODs, but it will if the type constructor is doing heavy-weight work.

Also, in some cases you must use init list, so you should always do it for consistency.