What are the differences between the following versions of Guitar Hero

Actually the only version being produced is the slim version ... you won't find a new -fat- version anymore... (unless someone sells them like diamonds). Anyways. The difference among the new models (slim ones) is based in their hard drive size. The actual versions are 120Gb and 250Gb ... but beware, this month Sony Japan will release new Slim versions in white color with higher high drives ... !!!

You can read further information on technical differences here: http://en.wikipedia.org/wiki/PS3#Model_comparison

The Xbox 360 version is different in that it features Kinect support. Here's an excerpt from the Destructoid review detailing the Kinect functionality:

Using Microsoft's camera accessory with the game is totally optional and serves to allow most of the game's basic commands to be given by voice. Kinect can be used to issue commands to squad members, activate special abilities, and change weapons, removing the need to open the game's power wheel, pausing the game and interrupting the flow of combat. Spoken instructions also extend to making dialog choices, opening doors, examining objects and pretty much anything else one would just press the 'A' button to do in a passive manner.

The marketing push for Mass Effect 3 states that the game is "better with Kinect," and it's hard not to agree. Voice recognition is very accurate, usually able to pick up commands even when speech is rushed. It's not perfect and does occasionally, rarely, fail to recognize a command but the system proves impressive nonetheless and it's easy to completely dispense with the power wheel altogether after giving it a little test.