We used Dr. Lula Lubchenco's growth curves for both clinical care and research activities. We did this because these were the most accessible and most widely used, and had become standard practice. Her graphs also come with weight-length or "ponderal index" percentile curves, which I have found very useful in my research.
Dr. Lubchenco's data were derived from babies born in Denver at mile high altitude. There was some concern that these babies were therefor smaller, rendering the growth curves lower, and resulting in a greater number of LGA babies if born at sea level. However, the mean weight differences between the Denver babies and those born at sea level were not found to be significant.
In short, I believe most people use the Luchencho charts for sizing newborn infants as well as for determining whether or not they are proportionately grown. They are regularly used in conjunction with the Ballard Score.