Thief is more of a pure stealth game than Dishonored. If Thief’s protagonist Garret is caught skulking in the shadows by a guard then its runaway time or game over. Dishonored’s Corvo however, can take the stealth approach or go toe to toe with enemies.
Both games’ protagonists have special powers at their disposal: Corvo has the blink power amongst others, while Garret can perform a special move known as the swoop. Corvo’s blink is a teleport power that is useful in stealth and combat and satisfying to use. Garret’s swoop maneuver allows him to quickly glide from shadow to shadow and is even more entertaining to use than Corvo’s blink.
But while in Dishonored you can pretty much navigate environments as you please, Thief places many artificial restrictions on the player. Only certain walls are climbable, for instance. Many times it feels you are just following a predefined path, while Dishonored is a more open game.