I would hang on a bit, new phones will be announced soon and there might be one that you really fancy or if nothing else the prices might drop a little on the ones you are looking at.
You couldn't go wrong with any of those to be honest, out of that lot I'd pick the Nexus 4 just for the updates and pure android looks amazing on it. I'm not a fan of the S3 but it does have the advantages of what FW said and gets loads of support. The One X is a great phone but I feel the JB update has sort of ruined mine as it was perfect on ICS, battery life is awful now and there is loads of little glitches.. I'd go for the One X+ which is a better version of the phone and has JB out of the box.