Udunno, but the more I play thief the more I want to pull out and work on dishonored's dlc, maybe even play the original story over again. Sooo many similarities to these two the further in I go. Stealth, theft, more lore than you can shake a finger at.
Graphics? Thief has it, definitely with the whole atmosphere pulling you in to the game thing too.
Sound? Both are great, but dishonored has my favorite theme song of all time.
Stages? Dishonored's are bigger but Thief's more detailed. I think thief also offers more ways of approaching any stage your in. Dishonored, your either going in stealth or trying to decide just how you want to kill everyone. If going stealth, its generally one route that is best. In thief, all routes are engaging for different reasons, all of them usually involve stealth.
Things to do? Both offer a overload of side things to do during stages though I think Dishonored offers more variety via side missions within the stages where as Thief always involves just stealing more things. Thief does offer large sections of the city to mess around in inbetween stages though.
Fine tuning your character? Both offer plenty of upgrades to equipment and abilities of characters.
Controls? Dishonored wins this, Thief feels very rough around the edges and for the love of god developers please always offer a toggle for head bobbing! Getting queasy over here playing thief...
Fun factor? You know... this is a tie to be honest. Thief is abit more repeatative but its also more engaging. The chattiness of the main character keeps me curious and progressing the main story has one eyebrow raised at all times. Dishonored has alot going for it but to be honest by the end of the main story I was ready for it to be done. Will have to progress further in to Thief to see if I'll feel that way by its end or not.
I like Thief's world better, a steampunk variation on the start of europe's industrial age. A city... built ontop the ruins of a city, really gritty.
Oh, and I'm amazing that the sex scene easter egg in chapter 3 of thief hasnt gotten alot of public attention. Seriously, the entire time your in the brothel looking at topless women entertaining men you can see these two moaning and going at it. And when I bumped in to them near end of the stage I was slack jawed at how blunt the scene was.
Not complaining of course, just suprised the media hasn't pounced already.