If I was you, I would get the most reliable phone.
Check my thread for a comparison between the Samsung Galaxy S3 vs HTC One X.
Samsung Galaxy S3 vs HTC One X
The SGS3 is the better device overall. It has the better newer screen technology called Super AMOLED (more vibrant and attractive colors albeit a tad exaggerated) and it comes with 2GB RAM, better quality antenna and a notification LED (very useful). Also TouchWiz 4.0 is extremely smooth (I dare say smoother than iOS, even PhoneDog agrees with me: Samsung Galaxy S III Review Part 1 - YouTube
). Also it got (or will be getting) the official Android 4.1 Jellybean update quicker than the HTC One X. Samsung has a clear advantage with respect to developer support.
SpeedTest also showed that the SGS3 is about 10Mbps quicker in upload/download Internet speeds (3G/4G LTE). This means SGS3 has a better quality antenna.
Also the SGS3 is the best when it comes to Internet browser performance:
Camera quality is better on the SGS3 as well:
The HTC One X while still a good phone, has a very bad quality antenna, making some batches of the HTC One X not able to connect to the Internet properly. Also, the design is not very ergonomic (it feels bigger than it really is because of the awkward placement of the power on button and jutting edges).