Dirk’s hair is softer, with a piece of hair coming down to the middle and his cowlick being more emphasised. The middle piece of hair in Ult Dirk’s sprite is styled more straight to mimic Kamina’s from Gurren Lagann. 

John’s hair might look more like fire, but it’s more windy/cloudy- I primarily used this base sprite when redesigning his godtier. 

Rose and Roxy are both drawn with more messier (or fluffier in Rose’s case) hair- two pieces on the side stick up to resemble cat ears. 

Dave’s hair is just a little bit messier, but overall smooth- his bangs swoop the same way Dirk’s does, but lacks the piece of hair that’s in the middle, as his bangs are brushed to the side. 

Jade’s hair is more wild, and similar to the Lalonde’s, she has two pieces of hair that sticks up to resemble animal ears, but in her case, it’s more doggish/wolfish? 

Jane’s hair is more curly, fluffy. Bangs a bit more on her forehead, and being more curled.