A PV stands for Privado and can either be a small private apartment with 2-5 ladies or something bigger like Esmaralda Vip which might have as many as 15 ladies available.
There are more than 100 such places in Buenos Aires, many on the same streets and sometimes same building. The services, or practices as well as; quality of the ladies and the price they charge vary very much from place to place, but also within the place with each of the different ladies. It is always better to be very respectful, relax and generous with the ladies.
Being that the PV’s do high volume, and ladies work different shifts, it is sometimes (especially during lunch and early evening hours) hard to find the lady you saw and liked on the internet. Same apply to lady that might show up in your hotel. Also when a PV gets hold of a hot lady, they will feature her pictures for moths after she left.
Of course all the photos you see are retouched heavily, to assume 10% Photoshop on each lady is a big mistake, for any lady on any site, also in the USA. As a photographer, I can tell you that 10% and a covered face, can make any lady a contender for a Playboy Cover Girl. The average photoshoping is more than 10% or even 20% in the crucial areas. The owners of some of the internet sites are known photographers and digital artists here and they alter the photos in such ways that make the ladies appear very sexy on the internet. It is true that in Buenos Aires there are many sexy ladies and many of them work in this industry, but very few are as sexy, as their pictures.
Some of those PV’s are really nice and the service (especially if you tip the lady a small amount) might be excellent. I would recommend you check

where the foro is in English.
One advice; stay away from the very cheap Pv’s some are very shady, those that charge at least 200 pesos for 30 min are much better. The price for one hour is usually only 50-100 pesos more so it might be better to stay longer.
If I were you, I would gather a list of 5-10 decent places and go there to check on your own. Calling a lady to your hotel involves taking a much bigger chance to get disappointed and it also cost more, and gives you no choice.
You can also help yourself by having the hotel receptionist write for you in Spanish next to your English version a list of 5-10 questions which you can show to the madam at the PV and communicate with a pencil and paper where the madam does not speak English.
If you send me a private message I could get you a better sense of direction.