Miller's World isn't actually (on the face of it) that bad an option. It has free water, a breathable atmosphere and organics. Everything, in fact, that's needed for Plan B to go into operation.

>  “Look,” he said. “Dr. Mann’s data looks promising, but we won’t get
> there for months. Edmunds’ is even further. Miller hasn’t sent much,
> but what she has sent is promising—water, organics.”

Not only which, but if they could get a viable human colony running then the world actually presents a unique opportunity since (due to the time dilation) the colony would be growing at an incredible pace relative to the time passing on Earth.