I guess it would depend on the age group of those voting. If you were looking at a whole-school vote, you might have younger students who hadn't read LOTR yet, but had read the Hobbit, or people who weren't big readers who had read the Hobbit when they were younger but never gotten around reading LOTR. In terms of language, the Hobbit is easier to read, so chances are more people have read it. And because a lot of people read it before LOTR, chances are that it's their favourite because it occupies that special place of being the "first"...
So while I personally think LOTR is better, if you are looking at people still at school, I suppose it's not really surprising.
(Where about's in Australia are you?
I know of two PLCs off the top of my head... Just curious
)