If the pins is given label, the benefit is that it can be used e.g. in filters:

Identifiers are used for defines in pin_mux.c so in case there is need to access particular pin, you can use this custom identifier (in menu Edit | Configuration preferences enable "Generate extended information into header file")
/*! @name ADC0_DP1 (number 14), MY_BUTTON
@{ */
#define BOARD_MY_BUTTON_PERIPHERAL ADC0 /*!<@brief Device name: ADC0 */
#define BOARD_MY_BUTTON_SIGNAL SE /*!<@brief ADC0 signal: SE */
#define BOARD_MY_BUTTON_CHANNEL 1 /*!<@brief ADC0 SE channel: 1 */
#define BOARD_MY_BUTTON_PIN_NAME ADC0_DP1 /*!<@brief Pin name */
#define BOARD_MY_BUTTON_LABEL "MY_BUTTON" /*!<@brief Label */
#define BOARD_MY_BUTTON_NAME "MY_BUTTON" /*!<@brief Identifier name */
/* @} */
This can have big benefit if the same application should work on more boards/processors (where the pin can have different name and thus different define) so it is not necessary to change the main application, because you can use constant that is independent on given HW.
It also does the code more readable.
Regards,
Libor