I definitely vote for rooted hair. It is way more dynamic... sculpted hair looks very toy like and almost oily. I think Hot Toys has been doing rooted hair very well now for some time and even some of my Triad figures have really good rooted hair (Jade Van Helsing for one).
I think they can pull off a rooted hair that works and maybe even fit a helmet all in one go but I would settle for two portraits, one helmeted before her reveal to the Witch King and then one with quality rooted hair. If their proto-types fail miserably than sculpted hair is preferable over terrible rooted hair but only as a last resort would I want to go this route.
After a number of good Hot Toys releases with rooted hair, I felt a bit disappointed by Baroness' sculpted hair, it seemed like a big chunk of soft plastic and makes her look toyish, still a cool figure but not as cool as she could be.