Female perspective:
Slap: Calculated thoughts, mental pain, hurts your pride, and puts you in your place cuz you're a little bitch...
Punch: Burst of anger, physical pain, hurts your face, puts you in your place because you just got knocked the fuck out..
It's kind of like calling someone a piece of shit rather than telling them to fuck off.
A piece of shit is the lowest of the low, they just called you worst that dirt.
Fuck off is just a stupid burst of anger, trying to 'get back' at you in a fucking rude way.
Personally, I feel that girls do a good enough job with the verbal insults, so if I had (and have had) to choose, I'd punch her in the fucking face. I don't need to insult her with a slap that isn't even gonna do much damage. Besides, I'm not a good slapper, I can't get the speed that those guys in the vids can, and I don't have a big enough palm make a real effect.