That title is completely misleading, of course. We NEVER have to choose between a book and its movie. The answer is always, “Both, please.”
That said, now that my kids are old enough (in our world, at least) to have tried out plenty of both, I conducted a little interview with them to get their take on books that have been adapted into movies. First their answers, then my comments.
Note: I asked them these questions separately, so no one knew anyone else’s answers. I have no idea if this is important to my oh-so-very-scientific findings, but I thought you should know.
1. What do you usually like better….book or movie?
Ellie: Mostly the book basically because they actually can talk about their emotion without having to act it out
Scott: both the same
Lucy: Normally the movie because I can see what’s happening
2. What is better about a book?
Ellie: They can do a lot more details
Scott: Books generally have more details than movies do.
Lucy: Because sometimes I imagine what it looks like and then when I watch the movie it looks totally different.
3. What is better about a movie?
Ellie: I usually get a better idea of what people look like
Scott: I think that movies are more exciting because you actually get to see the picture.
Lucy: Because you can see what’s happening
4. Let’s talk specific book movie combos:
First, which book is your favorite?
Ellie: Last one…eeeeehhhh….yeah
Lucy: The one where they all drink the potion that makes them look like Harry 
Then, which movie is your favorite?
Ellie: Honestly, that’s hard but my least favorite is the sixth movie. Maybe the fourth is my favorite, but I’m not sure.
Scott: Seven (Part 1)
Lucy: Eight, and my favortie part is when they go to rescue Luna and get trapped themselves [which I think may be in 7?]
Last, books or movies?
Series of Unfortunate Events (Book or movie?)
Lord of the Rings/Hobbit [Note: We have not fully read The Return of The King or watched the movie)
Which book is best?
Ellie: The Hobbit
Scott: The Two Towers
Lucy: I don’t know
Which movie is best?
Ellie: The first LOTR movie [The Fellowship of the Ring]
Scott: Second half of The Two Towers movie
Lucy: Not sure
Book or movie?
Lucy: Movies, because it is taking a long time for us to finish the last book
The Hunger Games (Which book is best? Which movie is best? Book or movie?) [Note: She hasn’t quite finished Mockingjay or watched the movie.]
Ellie: Mockingjay is the best book, but Catching Fire is a close second, Catching Fire is the best movie, I don’t know about book or movie…they’re both so good…I can’t tell
5. What book that you’ve read would you like to see a movie of?
Ellie: The Sisters Grimm and…Do your books count? Can I say that?
Scott: The Phantom Tollbooth
Lucy: Not sure
6. Do you feel like watching the movie before reading the book ruins it?
Ellie: Yes, but just because the book is usually a lot different from the movie
7. Does reading the book first ruin the movie
Ellie: Not really
There are several things of interest in their answers, and the most important of all is: I HAVE TOTALLY NERDED OUT MY CHILDREN!! I’m so proud.
What you see most of all here (other than the nerdiness) is how much the environment you raise them in, your values and opinions and how you spend your time, totally molds their own view of things. My kids may eventually change their minds, but right now, they have totally bought in to our love of books and words and powerful stories of all kinds.
My other observations:
1. Tyranical as it often seemed to them at the time, I have succeeded in convincing them it is always the right thing to do to read the book BEFORE you watch the movie. Victory is mine.
2. Ellie is way less decisive than her younger siblings. Picking one favorite was very difficult for her. A girl after my own heart.
3. It takes half of forever to read The Lord of the Rings out loud. We have literally been working on it for a year and a half and are only on the first chapter of The Return of the King. And yet, somehow, my older kids still like the books better than the movies. This shocked me. I would think they were only saying that to please me, but I can’t remember the last time they expressed an opinion just because I wanted them to.
4. My books totally count.
5. Lucy is a testament to the power of reading out loud. She LOVES the HP movies and can’t read to herself beyond simple beginner books, but still she prefers the books over the movies. And she is right. Those movies are delightful, but nothing can touch the books.
6. I agree with Scott. There should be a much better movie of The Phantom Tollbooth. The one that exists is awful. I didn’t even tell him about it.
7. Narnia! I knew there was something I was forgetting to ask them about. Ah well. Another day.