What is the hardest style of music to learn on guitar and/or bass?

I was thinking today about which style of music is actually hardest to learn, on either guitar or bass.
My gut reaction was to make the following two lists. They're ordered from hardest to easiest.

In time I plan to write a short intro to each style of music so you can get an idea of what's needed to learn these styles of music. (Links will be added to the list as I make the posts.)

Guitar:
EASIEST TO LEARN
Blues
Pop
Funk
Folk
R&B
Rock
Metal
Jazz
Classical
HARDEST TO LEARN

Bass:
EASIEST TO LEARN
Pop
Blues
Rock
Metal
R&B
Jazz

Funk

HARDEST TO LEARN

First thing I wanted to mention: You'll notice the order isn't the same. Funk is usually much harder to learn on bass than guitar, because it often involves slapping, popping, which are some of  the more advanced techniques for bass. By contrast, a lot of guitar work in funk tends to involve strumming the same chord (or very similar sounding chords).

I also didn't list classical for bass, since you don't often hear bassists playing classical music, whereas classical guitar is a genre and art form in and of itself, one very different than the other styles of playing.

If you disagree with my list, that's understandable. I'm not 100% sure about the order - I think an argument can be made that the hardest heavy metal songs are more difficult to learn than the hardest jazz songs, for example (but I think you need to know more theory -  a lot more - to play jazz than you do metal). I tried to answer by thinking, "In general, which genre requires more practice, more knowledge, and greater technique?"

As I said, I'm not totally sure about this. But if you were learning guitar and wanted the easiest way to get started, the blues might be your ticket. I don't often teach blues first, but that's based on student preference more than what's easiest to learn.