I'm not qualified to distinguish between the two, but, maybe a discreption of behavior will help. Took more than twenty shots as this guy seemed to like the sound of my D800's shutter and kept coming in closer to me.
See next three images of this same thrush as he/she came closer.
Cornell lab's eBird folks tell me it's a Gray-cheeked Thrush. See 'next' for a closer look.