local development vs. unpublished pages

I have a web site (www.visiblelightphoto.net) which is hosted, and I want to do some major revision to one section of it. Is it better practice to do the development on a local installation and then upload it, or to do it online and just not publish the new pages until I’m satisfied with how they look?

If it’s better to do the development on a local installation, do I download a backup of the entire site, make the changes, and then migrate the new improved site to the host? (If so, what’s the best way to do that?)

Or is there a way to easily upload just the new section?

I’m a bit of a newbie at this; I’ve migrated one local installation but can’t remember exactly what I did – and that was for a totally new site.

Thanks!
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