For me, it's the easiest. I've been pretty much exclusively inking since I got out of high school, and no longer had an art teacher driving me to do different stuff. I have taken up watercolor in the last couple of years, but ink is still my comfort zone. Thanks for the compliment.
I agree ink can be difficult and you did a great job on this sketch. I feel the same about watercolor and any medium that is instantly permanent. You really need to know what your doing. This is why I personally love using oil paint... I like to take my time when painting and let my compositions evolve, and with oils I can just scrape the canvas off and redo entire sections even a day or two later. Makes it more enjoyable for me to have the flexibility to go back and hit "undo" if I want.