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A const takes up a bit more in RAM if it is used in the program (it does not take up space by the mere declaration).

Definition of hardware pins is not usually redefined later.

For Digital pins either can work - such as:

For Digital pin numbers contained in variables, either can work - such as:

A lot of it comes down to personal preference, however it is clear that #define is more versatile.

Instead of using `int` type,

#define true (boolean)1
#define false (boolean)0

Instead of using `const bool true = 1;` and same for `false`

#define true (boolean)1
#define false (boolean)0

There is an interesting Arduino Forum thread that discusses other ways to decide:

#define vs. const variable (Arduino forum)

Excertps:

Code substitution:

#define FOREVER for( ; ; )

FOREVER
 {
 if (serial.available() > 0)
   ...
 }

Debugging code:

#ifdef DEBUG
 #define DEBUG_PRINT(x) Serial.println(x)
#else
 #define DEBUG_PRINT(x)
#endif

Defining true and false as Boolean to save RAM

Instead of using `int` type,

#define true (boolean)1
#define false (boolean)0