Sorry for bumping this thread but just thought I'd put my input in.
My sister is currently in Year 9 at Church High, she's been there since Year 7 and she's been very happy there and has loved her time there. So of course she is devastated that it's now merging with Central. We all are as she had a bit of a rough time in her primary school and was extremely unhappy there so we were pleased that she settled into Church so well.
She isn't going to be returning when it becomes Newcastle High School for Girls in September as we do feel that it is pretty much a takeover by Central rather than a merger. As mentioned above, Newcastle High appears to have very different ethos to Church High and is going to be a school for academic high flyer's, pretty much like Central is. My sister is bright but not overly academic and can be a bit sensitive and shy so we feel a pushy academic environment will not be for her.
She is going to be going to Westfield for her GCSE years and presumably A Levels if she wants to do them. The building is old, however as mentioned above the girls do seem happy there and it appears to be a very nurturing school. From what my mum and sister have also said, it isn't a pushy hothouse sort of school and whilst they encourage girls who are academic, they don't leave out those who aren't. Pastoral care seems good and yes, it's a very small school which might put off some people but this would be perfect for my sister.
My sister is of course sad that she has to leave Church High as it will be no more soon but she is adamant that she doesn't want to go to Newcastle High School for Girls and is looking forward to going to Westfield.
As for which school is best? Well that depends on the child. If you have an outgoing daughter who would thrive in a more pushy atmosphere then Newcastle High School for Girls would probably be best. If you have a quieter, less academic child then Westfield would probably be better. Obviously if your dd is only going into Reception in September it might be hard to predict what category she would fall into.
I really do feel you need to visit the schools in person though.
Have you considered Newcastle Prep school? That has a good reputation, although most enter Royal Grammar School for Year 7.