You guys are saying basically the same thing. Power runner or not, Murray ran hard and looked to deliver punishment at the ends of his runs. It was fun to watch. He's not the same kind of back as a Marshawn Lynch, though, which is what Fuzzy's basically saying.
As for Synjyn Days, apart from having a cool name, I think he's an interesting cat. He's got good balance, but runs with that weird loping style that makes him look sort of out of control. Listening to him interview, he's very respectful and sounds the part, at least, of a Cowboys player.
I don't think he's special enough to make it, though, but you never know. The more I listen to the coaching staff, despite what I'd like to see happen with this current group of backs, I think we're going to see a heavier dose of Dunbar via play calling that takes advantage of him in the screen game. And I think Randle and McFadden are going to be expected to get most of the touches. Williams, who I'd like to see really get the chance to compete, sounds like an afterthought every time Jerry or Jason talks about him. Which is a shame, because I'd disagree with the OP that we don't have a back on the roster capable of running with any power.
http://www.dallascowboys.com/video/2014/08/16/ryan-williams-i-needed-play
I can't help it. I really like the dude. Both how he runs (that cut to his right is pretty vicious, and he's capable of getting his pads low quickly for contact), and his attitude. He's a guy who brings an energy with him on the field and he's got his priorities completely straight off the field in the clips we've seen. And he's physically very gifted if his body could just hold up.