Please, Please, Please give me Merida's hair.... C'mon how is that even a battle take a look at the movement, the volume and colour in that red head...My hair is as curly as hers but it lacks volume and plus the hole red, It's just gorgeous. Who cares about all the healing properties in rapunzel's hair, plus is straight and way to long (Your setting yourself for failure, if you know what i mean).
Take the curly hair, a pain to even draw freeform, and add volume, strands and bundles, which way is it curling, shine, shadow, wind movement, highlighting...oh, and then animate it.
I draw, paint, sculpt(too embarrassed to post my sculptures here)jewelry, ceramics, and in recent years have tinkered with animated art, and curly hair like mine, and hers is the biggest pain ever to capture. Unlike with stills, you can't just photoshop an "oops" out of the frame and then post it. It took me over a month to animate a four second clip of a mountain sunrise, and when I was done with it, realised I left out the shadows on the flora. Now, take that difficulty, then translate that to people, with their myriad facial expressions and movements, atmosphere and environment, then add thick lustrous long curly hair. The fact that they had to develop a program to make and control the hair alone says how great a task it was. Renderman, which is Pixar's baby, was used in both movies, but it was "Taz" created and used in Brave that makes Merida's hair the more difficult.