That's a very good question???

This is my oppinion: In the last 20 years I have come to the conclusion that there are 3 types of providers. First there are the brand new girls ages {18-22}who are like the fountain of youth and even a little scared for there first few calls. Second there are the {23-29} girls that know what they want and how to get it, and usually have that wild side to them. Third is the 30 and above Ladies that have a niche or something that their well known for in the industry and trust me they do. Dont get me wrong these three groups have there own way of being a 10 in appearance
and a 10 for performance in my way of ranking.

i use the subjective 10 scale, though i dont think ive ever rated lower than 6 )i dont remember off the top of my head)

Very subjective. A lady that I consider to be a 9 or 10, others may consider a 7 or 8. We all have different likes and dislikes.

Rating of appearance is very subjective, and arrived at relative to each person's own preferences.  I think the numbers available through TER's reviews are compiled and reflected as an average.  The value given for appearance can also obviously be skewed depending on exactly how you're greeted at the door.  A beautiful woman greeting you in a sexy little nothing might "raise" an appearance rating one or two points.

It is of course subjective, and the looks rating seems often to be influenced by the performance rating.  Very rarely do you see a 9 in looks with a 4 in performance or vice versa.  A lady might get a 9/9 in one review and a 6/5 in another, but rarely a 9/5 and a 6/9.  Although I do admire the reviewers who are able to stay objective about a provider's looks and not let their performance influence the looks rating!  I guess along with YMMV there should be a YOMV; Your Opinion May Vary.

A 10 is defined as "one in a million", and I take it literally.  Heck, I think most of us would pay just to look at one of those.

9--model material--let's face it, if you haven't worked in fashion you probably havent met one.  Girls with those looks don't "provide" to us plebes.  They get paid just to stand around and be scenic.

I wish all the grade inflation would stop--we're using half the scale!