A year ago, there was a firmware issue that made the WiFi card upgrade a worthwhile boost in power. That has since been changed in the firmware. At present, the WiFi card swap is a rather insignificant change. Antennas are the way to boost your range and signal integrity.
The stock wifi card has a 200mw boost and the upgrade option has a 800mw boost. are you familiar with how the FW update overcame these differences? im genuinely curious here.
from my past experience (i used to build the RF systems on cellular towers for a decade), 800mw will definitely outperform 200mw when a range increase and RF penetration is concerned. Only because 800mw is obviously more powerful than 200mw, and most issues a wifi connection has is distance and obstruction (trees/buildings).