Other coloring aside, both versions of the pic of this bird show distinct dark shadowing from the bill straight back through the eye---not a stripe per se, but shadowing nonetheless. This really appears to be a Kingbird, rather than a Myiarchus Flycatcher.
Western v. Cassin's v. Tropical? I'm not sure---in my world, when in doubt, go with the most likely for territory. Bill size and coloring of undersides are usually the indicators if territory is not definitive.
Newest bird: Slate-colored Fox Sparrow, seen during the Portal, AZ CBC