You are behind the Eight-Ball the second you start believing in a ranking system
The obvious pitfall for using numbers to rank a girl's beauty is I have literally seen one guy call a girl and 9 and another guy the same girl a 3. That won't change anyone's mind here.
The instant a person begins to rely on what other people believe is attractive for themselves, by definition they are practicing ego gratification. That in and of itself is not a bad thing but it is unnecessary and off-track. Psychologically, the root of this is self-insecurity and low self-esteem, often but not always compensated with over-confidence and braggadocio. There is no other explanation that covers all the situations.
In my experience, a lot of guys who play this ratings game do not discern between the illusion of a girl with make-up and dressed a certain way compared to chicas who don't. In fact, take away the make-up and a lot of these so called nines look very different. Experienced mongers know it's not what they look like when you take them home, but what they look like when you wake up next to them in the morning.
If I had to apply a ranking system, (gun to my head) I would say all my girls are nines to me, and it is irrelevant what another monger thinks. Looks might grab my attention initially, but then I immediately start factoring in all the other things that make a girl a pleasure to be around. Personality can be the attraction without a primary consideration of appearance. Basically, the girls who I end up with look the way they look, another guys 9 or a 3, I don't care.
Guys who say there girls have to be a certain number will cop-out and say they still want a girl with personality and all the intangibles but that she has to be a nine or whatever number, first. I got a newsflash for you. That is code for "I can only get it up if a girl looks a certain way". We are right back where we started. Self-doubt and insecurity.
The other cop-out is saying, "I use a number, but it only matters to me. " Newsflash #2: then you don't need a number which only has utility for comparisons with other hunters. Even if a monger believes he is using the system with like-minded mongers, for example, all their "nines" have blonde hair, blue eyes and big tits, then at least in theory you could be creating competition for yourself, which would counter-productive. Every experienced monger knows the best wingman's "nine" should be very different from your "nine", another fatal flaw of this ranking system, jajaja.
Finally, the absurdity within the absurd is a ranking of ten. If the scale is 1-10, then ten represents perfection, and no girl in the history of the world is perfect. Show me any female, any person, and my trained eye will call out an imperfection within seconds.
We will always be saddled with the common, the base, in this case using numbers to rank beauty. That is a less enlightened, less advanced viewpoint that creates unnecessary obstacles and restrictions designed to relieve the internal psychological conflicts of the mongers who use the system. They pay artificially inflated prices they themselves have created. Since all participants appear willing, I don't see the harm.
There are venues designed to attract guys who partake in this system, such as high end bars and clubs, where not surprisingly the prices are the highest for everything from the girls to the drinks.
A more enlightened conversation could go something like this. Mongerer Joe says, "I love my new girlfriend, she's just what I have been looking for. " Mongerer Bob, "What do you find so attractive about her"? Joe replies, "She weighs 400 pounds, and I love fat chics". Jaajajajaja Ostee Out.