After the initial sketch I wasn't sure how I would finish it, but as I got into the final I found myself drawing with an almost clinically clean ink line, completely open save for Superman's black hair, and coloring with a vibrant palette. There's probably more than enough darkness out there already, I reckon.
And while I am no expert, I believe a true Superman vs. Batman showdown would end quite quickly with Batman utterly destroyed in seconds, but that may just be my dumb logic speaking.