Here is my two cents on this and related issues based solely on my experience. By no means am I trying to be insulting at all to anyone, but rather answer the question honestly.
1. Tightness of a woman is related to three factors,
A. children (or lack there of);
B. body type as revealed most accurately by wrist size, height, and size of mouth,; and
C. Weight
2. Redheads in general are tighter than brunettes, but usually have less responsive nipples
3. Hispanics women are the most demanding in bed and reach orgasm fastest,
4. All but one of the multiple orgasmic women I have been with have been light skinned, blue or green eyed. Where as women of African, Hispanic or Mediterranean ethnicity I could only ring their bell once if at all.
5. The most telling sign regarding the sensuality and sexual drive of a women, irrespective of race, is well defined, wide philthrum, which is the space between the nose and the mouth.