Also, McKellen has a way of exuding menace just by being there which Holm doesn't. The less overtly menacing, quieter, more soft spoken performance would have made him seem that much more dangerous when the character was looked at in his entirety.

that Sophie broke up with her grandfather - who is her real grandfather and not an adoptive parent as they would have you believe - because she saw him perform a sexual ritual with an unknown woman and later found out that this woman is in fact her surviving estranged grandmother and that her brother also survived the car crash, all elements which are essential to the closure in her life. By removing all those elements out of prudery and so as not to associate the belief in the bloodline with "strange sexual rituals" and the fact that Saunière, a descendant of Christ, may have had a sex life, the filmmakers essentially eliminated the essence of the human drama in the book and left Sophie high and dry, without any other "family ties" than this weird adoptive cult and not even the promise of a date with Langdon. I mean, the poor girl! So that when a Central Casting granny comes out of the rank-and-file of the Prieuré at the end to announce "I am your grandmother!", we collectively ask: "Like, do you mean you are her actual grandmother on the mother or father side, or some kind of adoptive grandmother and we should care, at this point, because...?" The new, simplified and sanitized ending also eliminates the final mystery of the sarcophagus' last move out of Rosslyn and makes the last scene empty of all logic. The script also makes Fache into a bad guy who is also stupid, makes an enigma of Silas and totally eliminates Teabing's listening station as a major source of revelations.