Skulls of royalty

Tarbosaurus, despite being a relative of T Rex, actually looks a little more slender in the skull area.  I don't know the exact angles of the orbital fenestra and subsequent eye facing, but Tarbosaurus has a noticeably less stereoscopic ability than T Rex also, meaning the eyes face less forward in the skull than in T Rex. Compare, T Rex at the top, T. bataar at the bottom:

Sue at the Field Museum

Additionally, the slope of the muzzle in Tarbosaurus and T Rex is different. The T Rex slope over the nostrils being steeper and the frontal bone having a small dip which also makes the overall slope of the skull to the nostrils slightly steeper than that of Tarbosaurus. The dentary and surangular of the jaw are clearly larger in T Rex. Additionally, the palatal bone in Tarbosaurus juts much farther up into the view through the antorbital fenestra and orbital fenestra than it does in T Rex. Check it all out below, same order as above.

Either way, he's still a scary animal: