Extruder feedrate when loading and unloading filament
Loading and unloading filament through the LCD options is taking care of by G-code command M600. The options used when executing the M600 command define where the head goes and how much filament is extruded of which extruder. Apparently, there is a difference in calling the M600 command via the LCD menu or (un)loading filament through the Repetier application. 

The Firmware-based and LCD-controlled retract options are defined in Marlin Firmware file Configuration_adv.cfg (Advanced Pause). The settings for Repetier are probably differently defined than in the advanced configuration file; you should look them up in Repetier. It could well be that separate G-codes (or scripts) are used for this. E.g. G10 is used to retract filament as set by M207 (both length and feed rate!). G-code G11 does the opposite, it unretracts the filament as specified by M208.

To answer your question, yes, you need to alter the values of the constants in Configuration_adv.h for changing the speed when using the LCD to change the filament:

// (mm/s) Unload filament feedrate. This can be pretty fast.
#define FILAMENT_CHANGE_UNLOAD_FEEDRATE     10  
// (mm/s) Load filament feedrate. This can be pretty fast.
#define FILAMENT_CHANGE_FAST_LOAD_FEEDRATE   6