6 Days in Flagstaff, Page, Bryce/Zion area--advice?

I would suggest Bryce over Zion but I cannot recommend a campground. We stayed a Ruby's a few years ago during Easter Week and they had to plow for to get. Fair campground but the other facilities were over run with rude and obnoxious folks. There are public campgrounds around the Bryce area and others have mentioned them on the forums, so maybe a search would help find them.

I agree about the Arches, Canyonlands areas. Dead Horse Point St Pk is great, if you have 4X4 the Canyon is fantastic.