Been doing some research, info about a few ladies I'm interested and reading some of their reviews and what I found was 95% similarities of the details were the word "she's vocal"...

I say 'vocal' would imply actual vocalizations, including but not limited to onomatopoeia. That means the "oooohs, eeks, aahh aahs, a oh, yes yes, fuck me" are all considered 'vocalizing'
So, by definition of the English language I say "All of The Above" on this one, Alex. And yes, that is my final answer!

I know a guy who used to want me to bark while in doggy style... now THATS vocal. Lmfao  

While she is facing the wall, that hotel security is called.  Happened to me in Boston in an older hotel with some thinner walls.

volume. Loud or just a purr, it's the intensity  
of the moment. And the reality. IMHO anyway

Hehe I always worry that's going to happen to me. Stuffing my face in a pillow helps.

it's being in the moment and real. Animalistic vocalization or dirty talk... all can fit if they are legit.

...from the soft moans of pleasure and almost sub-vocal purring, to where her neighbors know my name

The auditory equivalent of an involuntary muscle spasm.  Not something you consciously did, but a sound your body gave up in the heat of the moment.

In general, I do love to hear a gal moan, groan, and (if a highly secure area) scream with delight.  I don't care if it is genuine or not as long as she can pull it off convincingly.  This is after all audience participation theater, is it not?

For me being vocal means telling the client I like what he is doing and moaning and yessss that feels amazing. If he is not doing it correctly I will guide him through what feels good for me particularly also if the client is happy I want him to show some sort of response so I am pleasing him or guiding me through what might work for him. I think it goes both ways to pleasuring the client and the provider.

In the heat of the moment I can hear my dick throbs, my heart rapid beating, minds losing and when all the tension been released, I can hear my whole body shudder, shrivel and shakes...

vocal is usually faked. Screaming, biting on pillows, none of it seemed real.  I have no doubt that some providers actually do have orgasms and get vocal when they do. But I've had providers start to scream or make other loud noises one minute after we start intercourse.  

When she screams your name out and its the wrong one

...i feel there should always be that intimate vocal exchange..sometimes it might even get loud...but i HATE that fake OMG!! loudness that some girls do because they think its what guys like and thats want do in porn vids..nothing makes my cock shrink like that first OMGGGG...