When it comes to rooted and sculpted hair, I generally stick with the Barbie and Ken rule: Rooted hair for females, sculpted hair for males.
Now of course, there's always exceptions; it just depends on the hairstyle and the character. There's some female figures where sculpted hair looks better than rooted and some male figures where rooted hair looks better than sculpted. Generally, I'd say the longer the hair, the more likely it should be rooted. However, this isn't always the case. For instance, Thor has longer hair, but I think sculpted hair looks better than rooted hair.
It just really depends on the sculpt and the hairstyle as mentioned. In this particular case, I think rooted hair may have possibly been a better route to take for Doc.