I think one of the Suns problems is that they have both of them. It might be necessary to commit to one and move the other for full development to occur.
I'm afraid that is probably what needs to happen. Drafting both of them doubled our odds of getting a good PF from that draft but needing to move one of them so the other can really settle in is something that's been at the back of my mind since that draft. Ideally they'd both be playing well enough that trading one would mean getting some value in return but that's not the case right now. They're both young enough that they should have some value to another team, it's a question of how valuable someone else deems them though. I don't think they'll be able to get a lottery pick for either of them but they could probably deal one on draft day for a late 1st but we don't need more draft picks.
Chriss seems to have regressed this year with Bender challenging for more playing time. He did well last year when he was basically the only PF on the team while Bender was injured. Bender on the other hand has improved from his rookie year and is trending upwards overall, so he'd be the one I'd prefer to hold on to.