I would categorize them as Gunn's being Third Stream while Hagans belonging to the Traditional family. Don't feel bad Bluegrass and Country have to share as well. On the other hand Gospel has different categories. Even the Rock category broke it down with Metal and Alternative as sub-categories. On the plus side, jazz has more categories than most - a total of six.
Blues only have two.
In the end it's peers voting on their peers. I'm eligible to join the Academy and vote. All I have to do is send in my money. Then I can vote on the artists that I feel are worthy. So, since I didn't spend the bucks and I get to write this for free, here are my five nominations.