The main reason that I can think of right off, Bombadil, is that PJ slightly changed some of the quote to make them more understandable/fit better.
For instance: When Aragorn tells the fellowship that they must move on because "By nightfall these hills will be swarming with orcs." the original line ( I'm guessing that means what PJ was going to put in, perhaps it's straight from the book? I don't have the time to look it up now :/ ) was "By nightfall these hills will be fair teeming with orcs.". I've gotta admit, I like the 1st better. I thought PJ did a great job with even using quotes from the books (although maybe adjusted slightly), but everyone has a thing that bugs them more than others.
