None of them are bad! Gorgeous park. South Nicolett Bay...the sites that back up to the water are in great demand.
IIRC, all of North nicolett bay are no-hookups, but we like them too. Be aware, Wisconsin does not allow Generators, so keep that in mind. I can't recall it I've stayed in Tennison bay or not, but I've ridden my bike and scooter through there, and it is very nice.
I've been to this park probably 10 times over the last 15 years, and it is one of my favorites! Huge, well kept, pretty waters, golf course, lots of trails that are well maintained.
"If the women don't find you handsome, they should at least find you handy." - Red Green