It is useful to compare the two devices as they are so similar and picking the better of the two takes a bit of analysis.
The HTC One X was released a few months earlier than the Samsung Galaxy S3 and so took some shine away from the Samsung Galaxy S3. The Samsung Galaxy S3 however has a huge following so was always going to sell well regardless of what was already on the market.
The HTC One X is larger sized phone than normal, yet it is still slightly smaller than the Samsung Galaxy S3. It seems that this is the trend of phones now, to be bigger than the usual size.