Deus Ex Human Revolution vs Dishonored

First lets be clear on one thing, both are exceptionally good games, both have a very good ( in my not so expert opinion at least ) stealth game mechanics, and in both games you can choose whether to play stealthy or just plain brute force.

In your case, I believe either game would suit your needs, it will come down to what setting you want to play. Do you want to be badass ninja type character assassin in a steampunkish victorian England or do you want to play a badass cool security agent in a cyberpunk dystopian futuristic world ? Both games have rich lore, though Deus Ex in my opinion has a much more deep background storyline ( as it is an older franchise ) and is more fleshed out.

It also depends on the time you intend to spend on the game. I own both games on my Xbox 360 and it took me significantly longer to complete Deus Ex: HR as it is more open ended and in my opinion has more content. But both games are very addictive and fun .... I wish you good fun with either of them.

liked the atmosphere of both.
both games have several ways to accomplish missions.
dishonored kind of puts emphasis on using your powers to complete a mission where deus ex doesnt feel as much that way.
both are ghostable and pacifist.
to me what makes dishonored slightly more fun is your ability to climb everything.
but deus ex if far longer gaming experience.
but if youre wanting to go rambo i found both to be fairly unforgiving. though i played on highest difficulty.

Two of my three favourite games, cool.

I've done a ghost-pacifist playthrough in both. In terms of stealth, I'd suggest Dishonored. I believe it is a lot more enjoyable.

On the subject of achievements, since you mentioned them, Deus Ex has a million ways to miss the no-alarms or pacifist achievements (which happened to me). Dishonored has the benefit of showing you exactly how many people you may have killed or how many alarms were rang at the end of each chapter, thus allowing you immediate replay to fix it.

Deus ex doesn't have mission replay and you probably won't know you fucked up before the end of the game.

Deus Ex HR

Hum, hard choice.
I finished both with no kill/alarm and i enjoyed both.
But you'll have more playing time with Dishonored.