Neither is a real favourite of mine, but out of these three, my preference would be Brown.
* I think Murray's ceiling / upside is too limited
* I think Chriss's floor is too low (too high a risk)
Brown I think has the right floor/ceiling ratio. He's high a high upside, and yet has enough talent physical and in terms of skills) to ensure he should have minimal risk of being a major bust - should at least contribute SOMETHING in the NBA. Chriss and Murray - I'm not so sure.
That's pretty much how I'm looking at it. Brown has, IMO, one of the highest ceilings in the draft. If he can shoot better than some believe (I think he can), he I think he could become a Kawhi-Lite. Plus, chances are he bottoms out as a versatile defensive wing who can't shoot that well. More Tony Allen like floor. And that's a pretty good player.
If Chriss flops, it could be epic. Same with Murray, though I think he could make a career out of spot-up shooting. Bender to me has super high upside, but there's such limited stuff to look at with him that it's hard to know whether his skillset can be NBA caliber.
If your looking for a relatively low-risk/high upside guy, you go with Brown or Dunn, and considering our glut of guards, it's hard to pick Dunn if we don't trade a guard or two.