If it's just for gaming, I would go with the 27" as it has a better response time and refresh rate, but if you're going to be doing more than gaming, and don't mind a 2cm space between the images, then the dual monitors can be much more productive.
I have an Asus 27" LED HD monitor and love it.
"Where do you put the bayonet?"
Chesty Puller (upon seeing a flamethrower for the first time)
I am all in favor of keeping dangerous weapons out of the hands of fools. Lets start with typewriters.
Frank Lloyd Wright
Cain's Lair, "Great Games, Great People", "You'll come for the games but You'll stay for the people", "You'll come for the games, stay for the people", Cain's Lair Brick Device, any and all imagery which identifies the Cain's Lair brand, and markings thereof are protected under law. Usage without permission is prohibited and hereby withdrawn. All other trademarks and copyrights are property of their respective owners.