They're all different fields with their own complexities. If there is one that's harder than the others, I'd suggest Technical Artist would probably be the one, given you need a handle of coding, or at least scripting as well as art.
Just to weigh in my opinion the hardest to be good at is going to be a technical artist, purely because by being more technical orientated you have to know waaay more fields beyond the scope of just what you see eg coding/scripting/integrating. Which in turn means keeping upto date on improvements on each of the above.…
Yes i agree with you that's why i said it may become technical but did not expand that. At the end of the day every field is interconnected and all represent a challenge, it terms of difficulty an equal challenge. The only reason that i said that a Technical Artist could be the hardest one is when considering a "normal…