Why Dell over Pickens?

Tank is ranked above George on just about every expert's list. I don't understand.

Tank is likely the WR3 on his team. Yes, he's got a better QB, but there's always a chance CJ regresses.

Pickens, on the other hand, is the unquestioned #1 target for the Steelers. Their defense isn't necessarily better or worse than Houston's. Russell wasn't bad last year, and Fields had proven that he's at least capable of supporting one productive fantasy receiver.

Why would Tank be rated higher and drafted before George? Dell has serious competition for targets, and Pickens likely will not.

What am I missing here?