I use
Lunarpages for 10 sites and just love them...but any reputable host will allow you to set access permissions for the folders and files.
Another method might be with the software used for the work: I use Dreamweaver and it has a feature whereby I can give access to certain areas to certain people.
Rely on Popularity, Price and third party reviews do decide on your Host.
Google for
reviews"web hosting" and similar searches, and you'll see a dozen or so at the top of alot of lists.
...just a few things to think about; hope it helps.