Well, to answer that -- I'm adept in prose or script, but the majority of my own spec work is in scripts. I'm a screenwriter first and foremost, and then a writer of pretty much anything and everything else. Script, to me, is just far more comfortable.
"Now I did a job -- and got nothin' but trouble since I did it, not to mention more than a few unkind words as regard to my character, so let me make this abundantly clear: I do the job... and then I get paid. Go run your little world."