Hmm...
Unity sounds interesting, but you have to buy into the Unity platform solution, so it's an investment. Also Unity has only a few of the cool features that make AGS special and easy to use. Unity would require more time with coding it seems, where a lot of it could be done with AGS scripting. Example: http://answers.unity3d.com/questions/31247/how-to-setup-a-typical-adventure-game.html
There's also MOAI that other adventure games are using.
Right now AGS looks best for adventure games, and existing games are working fine on different devices. Also I prefer AGS because it has better support from the community for an adventure game.
Unity sounds interesting, but you have to buy into the Unity platform solution, so it's an investment. Also Unity has only a few of the cool features that make AGS special and easy to use. Unity would require more time with coding it seems, where a lot of it could be done with AGS scripting. Example: http://answers.unity3d.com/questions/31247/how-to-setup-a-typical-adventure-game.html
There's also MOAI that other adventure games are using.
Right now AGS looks best for adventure games, and existing games are working fine on different devices. Also I prefer AGS because it has better support from the community for an adventure game.