I make my decision on B&W or colour before I look through the viewfinder. I compose the shot differently, depending on the genre. With Trevor's shots, I like the way that the colour one is composed, but I would have done a tighter crop on the B&W because of the reduced influence of the foreground and background.
This does not apply to the B&W, so I would have come in closer to the house and tree and reduced the amount of snow and perhaps the sky in the shot. Trevor is a touch closer in the B&W already, so he is moving in the same direction I would have.