Good points on both sides.
I see the value in reading the full books but I also think that even just a taste of a good story will spark the desire to read it again as an older child/teen/adult. And when that revistation occurs, I highly doubt she will be looking in the children's section for abridged versions. As a child, I remember reading some unabridged classics like
A little Princess and
Black Beauty but I also read lots of abridged versions of books like
The Man in the Iron Mask,
The Adventures of Sherlock Holmes, and a few more. I grew up and own the full version of all of them. So I don't know...
I am leaning towards just making sure that I have all the age appropriate classics available and get the others as she grows.