Too many women in porn try to fake it, and it's almost never good. They should just naturally do what comes to them. It would almost always be better than the annoying forced screaming or moaning.
There are more chicks that have real orgasms (not squirt or gush shit) during scenes nowadays than ever did in the past.
Allot of the guys do a piss poor job of fucking these chicks and they either spend half the scene pulling out or switching positions...
If you're into chicks having real orgasms during scenes your best bet is to find the chicks who do cum and match them to lesbo scenes.
Outside of that the only dudes who make chicks cum pretty regularly during scenes from what I've seen are Lexington Steele, Mark Ashley and Julian Rios.
As far as the fake moaning and screaming...the minute I see that shit...I turn the scene off. The only thing more annoying is some dude or camera punk babbling all throughout the scene.
BTW, if a person can't tell the difference between a real orgasm and a chick faking it...I would say they've rarely if ever made a chick cum in real life. The signs of chicks having real orgasms are pretty clear in most cases.