I'm used to Northern California, where the only regular Myiarchus flycatcher is Ash-throated: it's tougher in Arizona. I didn't get a good description of the vocalization, but I conjectured this was Brown-crested on the basis of the undertail pattern -- rufous all the way to the tip (tip brown in Ash-throated), and rufous extensive (very limiited in Dusky-capped). Arizona birder Rick Wright backed me, adding that the large bill and the extensive yellow on the underparts supported the ID of Brown-crested.