I feel like it doesn't change anything and if it does it is definetely not 1.5 multiplier. Here's what I gathered so far.
1. Player XP gain:
Kill: 50
Headshot (P90): 19
Knife in the back: 37 (right click)
Knife (right click): 13
Knife (left click): 3 or 4
Body shots / leg shots (P90): 3-9...