Between Murray and Choice, IMO it's Murray all day long. Choice fumbled deep in the red zone again this past weekend. If he's not fumbling late in the half to give up a fumble-recovery TD, he's fumbling away a red zone possession. There were reports of Choice being on the trading block last week. Obviously the untimely injury to F.Jones made that trade less likely.
Murray came in the game and ran hard, including good yards after contact. He only averaged 3.2 ypc, which isn't great, but he was a physical, downhill runner. I was impressed. And I say this begrudgingly as a F.Jones owner.
When Jones Gets back, it will be Jones and Murray, and I wouldn't be totally surprised if this isn't closer to a 60% jones/40% Murray timeshare once Jones returns. They flat out cannot trust Choice with the ball with regularity. Jones has shown yet again this season that he is injury prone. The separated shoulder, now the high ankle sprain, and we're going into week 7. The cowboys will use Murray more to give Jones fewer reps and keep him healthy.
Whether you should use a 1st waiver priority is a different question. You already have the Torain/Shanahan/Hightower problem. You will be able to use Murray this week and next as a reliable flex, IMO. But once jones gets back it will be tough to say whether Murray will get enough reps to be a starter (even though I'd expect him to get at least 10 carries per game). Of course, if (when?) Jones goes down again, you've got a starter on your hands again. Whether something won't happen next week e.g., Chris Johnson going down for the year, and you would wish you'd saved that No. 1 waiver priority for Javon Ringer, no one can tell. Personally, if you've held it this long, I'd be reluctant to use it on a guy who is only guaranteed to get starters reps for a couple weeks. (Of course, he could also blow F.Jones out of the water with those reps, so who knows.)