For me, relative difficulty is not about genre. It's about arrangement and overly busy music.
I have a sliding scale with the two extremes being:
Simple = easy
Busy = PITA
Some genres are inherently busier than others, of course. But in most any genre, a good arrangement is soooooooooooo much easier to make into a great sounding record. It's a pity that I get to work on so few really good arrangements (even my own, I'm afraid). I think it's gone out of style.
Regards,
Brian T