Assuming I was conscious of the opportunity to be anything else? No idea. They're all awful beyond words.
However, assuming I'm indoctrinated enough to be all YAY THE IMPERIUM LET ME SALUTE THAT FLAG BEING A SOLDIER SURE IS GREAT I CAN'T IMAGINE A BETTER LIFE THAN THIS NO SIREE, I'd go Inquisition, hope they don't lobotomise me on the way, hope that I live long enough to hide safely somewhere.
Or maybe be a Rogue Trader. Work anonymously on a ship somewhere - create no waves, run at the first sign of trouble.