Well, that depends... will I be assigned to one of the 3 destroids that get blown up AGAIN AND AGAIN every time the zentradi attack the ship?
Seriously, it depends on WHICH destroid.
I'd take a Monster assignment in a heartbeat. They aren't even deployed most of the time, and they have enough armor to withstand more of a beating than just about anything else. But if it's a Defender, I'm placing better odds on the Valk.