Uh... no. The nerves associated with the genitals are somewhat different, and it is in those differences that pain is registered in unique ways. It's not a matter of surface area.
Testicles are more highly tuned to differences in pressure and constriction (thus how your sack can expand and shrink depending upon various temperature conditions) and when too much constriction or blunt pressure is applied, the testicles release a hormone rapidly that causes depression and a flight mentality. It also sends nerve shockwaves through your body, thus the empty, horrid feeling you get in your lower abdomen.
The primary registering nerves of the vagina are much the same as the shaft of the penis and the head of the penis at certain points. Getting kicked in the cunt is like getting kicked in the dick. The pain is nowhere near the tour-de-fucking-ARRRRGH that it is when you get a smack (even a light one) on the balls because there is little to no hormone release when your dick gets smacked in an unpleasant manner.