You're right - that is an interesting question.
Stewart hasn't played terribly well against the Packers in the past, and may lose some carries to Richard Huntley. Neither Coles nor Morgan look like terrific starts this week, either, although Coles could see significant action if Miami grabs an early lead.
In the end, I think it comes down to your own game this week. If you're playing a team that you should be able to beat, play Stewart. He'll definitely get you some yards, and a score isn't out of the question. If you're the underdog, I'd go for a player with greater risk and reward and start Coles, hoping the Jets play catch-up all day.