Well, since you’re wondering, the following is an edited excerpt from Graydon Carter’s “Editor’s Letter” titled Roman Holiday from the October 2005 edition of Vanity Fair (my sincerest apologies to the mods and admin of the SDMB if this excerpt violates any of their copyright agreements) (from here):
*"Now is as good a time as any to review why the man whose good name we were accused of besmirching and on whose reputation the jury had to place a value could not be in the courtroom that week. In early 1977, Polanski, then 43, had been hired to photograph some girls for a French fashion magazine. He was directed to one young girl, whom he met with her mother at their home in Woodland Hills, in Los Angeles. The girl was 13. She had a dog and a pet bird. “I was rather disappointed,” Polanski wrote in his autobiography. “[She] was about my own height, slim and quite graceful, with an unexpectedly husky voice for her age—a good-looking girl, but nothing sensational.”
A week after that first encounter, Polanski drove back to the girl’s house in his rented Mercedes, and the pair went for a walk in the hills so that he could take some photographs. According to the girl’s subsequent grand-jury testimony, he told her to take off her top, and he shot her breasts. A few weeks later Polanski turned up at the house in Woodland Hills …{snip } … Polanski poured her a glass of Cristal champagne from a bottle he had found in the fridge and refilled her glass from time to time. Polanski then led her outside to take pictures of her in a Jacuzzi. He produced a yellow vial, and they each took a part of a Quaalude. She said he urged her to remove more and more of her clothes until she was completely naked… {snip}… When he attempted to grope her, she said, she rushed out and went inside to dry off. Polanski followed her into a bedroom, kissed her, and began to perform oral sex on her. She said she asked him to stop several times, whereupon he began to have intercourse with her. When he discovered that she was not on the pill, Polanski, ever the gentleman, withdrew, and then proceeded to sodomize the 13-year-old. Afterward, as he drove her home, the girl recalled, Polanski said: “Don’t tell your mother about this, and don’t tell your boyfriend, either. This is our secret.” *"
Vanity Fair Oct '05 (pp 88-92)
All bolding mine.
According to this account, keeping in mind that IANAL, I’d say the difference is coercion, coercion involving drugs, sexual assault, sexual battery, statutory rape, and vaginal and anal rape. Not having seen the movie, I’m not sure if this is a profound enough difference to warrant attention by you, but I’d say it’s a fairly significant difference.