Ours had/will have very little imput. Children of 9-10 (as they when they start looking around and the forms are actually filled in) cannot make an informed decision about where to go to school. That's our job as parents.
We were definite that our 3 would go to the same school, so when we had to apply for our eldest, we were clear from the start that it was us the parents making the decision for all 3 of them, rather than our daughter deciding. Otherwise it would have been 'how come SHE got to choose and we can't'.
The friends business is a red herring. Yes, in the initial days it is lovely to have some familiar faces around, but children make new friends so quickly. Within a fortnight of starting, our eldest wasn't mixing with any of her old primary friends, and her brother has followed the same pattern. I've known parents (or their child) choose a school on the basis of where friends are going, and in the end they've moved on from those friends very quickly indeed.
I would echo Freckle's views - have a look around all 4 schools with an open mind. 1000 pupils really isn't that big - my children's school has over 1600 but doesn't feel huge. It still has a lovely community, 'family' feel to it.
I don't think it's unreasonable for parents to choose. Children have a different agenda, they want to go where their friends 'might' be going, or where the school dinners were nicer on their trial days, or where the uniform is (or isn't) a certain colour, or because they liked the look of the dance studio or whatever. Parents are looking for a school for 7 years which will hopefully bring out all their child's potential - my 9 year old is also starting secondary school in Sep 2008 and there is no way I would hand that decision over to him.