The problem is that you also need to find out how the buttons are mapped, and if it is easy to make them work with most apps, games and emulators.
The great thing about the Sony Xperia Play is that it does directly support a lot of apps, games and emulators, and can easily assign keys for others.
Personally, rather than getting a dedicated tablet with game controls I would buy a Sony Vita at the moment.
And I agree regarding the Playstation license. Sony could really get in on the Android gaming market more if they made one of their tablets an Android 4.1 tablet with gaming controls.