My personal opinion:
1. Design: The front design is nice, but I really don't like the back design. And the design is at the last of my list that I will look at, so I don't really mind with the design
2. Build Quality: Heard that it uses a brushed metal? Or is it still plastic material?
3. Screen: Tried out the HTC One X, YES the display is nice, but I'm very disappointed with the black level of HTC One X, so I much preferred with Samsung Galaxy S3 display eventhough people are complaining with it's pentile matrix.
4. CPU: Samsung Galaxy S3 packs 1.4Ghz Quadcore Exynos processor (HTC has 1.5Ghz tegra3 processor). In GSMArena benchmark, it beat the hell out of HTC One X and excel in BrowserMark means that Samsung Galaxy S3 is very2 good in browser department. Samsung Galaxy S3 win here
5. GPU: Still using Mali-400 GPU? Now that is old. HTC One X tegra3 win here.
6. Software: The Samsung Galaxy S3 is using the same Touchwiz UI 4.0 but with a little tweak+added features. Most of the added new software are just gimmicky, but it's nice to have something new.
7. Storage: This is the part where Galaxy S3 really beat out HTC One X. With 3 variant of storage: 16gb, 32gb, 64gb plus with MicroSD slot, Samsung Galaxy S3 win here. An option is always better.
8. The camera: The camera UI is still the same like my Galaxy note, but it packs with awesome features like what HTC One X have; Burst Mode and able to capture picture while in recording. Picture quality is still unknown. Samsung Galaxy S3 win here
9. Battery: Samsung Galaxy S3 has a removable battery, where the HTC One X doesn't have. Plus 2100mAh gonna provide extra battery life and I'm glad Samsung made a nice decisions with the battery. Samsung Galaxy S3 win here