I hired my current nanny precisely because of her daycare experience. I have four children with schedules, and I wanted someone with experience balancing the needs of multiple children and the willingness to follow reasonable procedures about cleaning up and getting them ready.
The most valuable quality her daycare experience gave her, in my opinion, was a really good sense of how to deal with multiple unhappy kids, or two people who needed something at once, or a messy craft project with multiple kids.
In your case, the nanny share candidate also has that experience, so it wouldn't be as much of a bonus.