I'm an artist who does both. I will never understand why "difficulty level" is even taken into account when it comes to art. I only care about what the finished product looks like, no matter how hard it was to get there. Why would it matter if the perfect color was mixed with paint or selected on a tablet? The end result is the same, the former just used a more primitive method to get to the same end.

And as far as people who think that digital art is "easy" just because you can select your brushes and colors and have an "undo" button, hand anybody who isn't an artist a tablet with a paint program on it and tell them to create their best possible artwork. It will end up being stick figures just like if you handed them a canvas and paint set.