When choosing between those three it totally depends on you and your team. Unity and Torque are more "powerful" but you really should have good progammers who know what they're doing while with Gamestudio you should be able to do anything you want with the scripting language...

But what exactly do you mean with "Adventure"? If this is about the classic point'n'click style (e.g. Monkey Island) I suggest you have a look at those two:

http://dead-code.org/home/
http://www.visionaire2d.net/cms/front_content.php?idart=3&idcat=2&lang=1

As you said you want to develop "fast" there's nothing that beats those two as you won't have to reinvent the wheel in terms of pathfinding, masking / making certain areas clickable and working out the game dynamics. At the same time you'll be a bit more limited in terms of what the engine can do so you have to find out if one of those two is totally sufficent. I'm not too much into the Visionaire engine but for a good demonstration of what Wintermute can do have a look at Mental Repair (as anyone liking such games should do as it's quite fun)...

Enjoy your meal
Toast