If you are calling the One X "real" just because of the quad cores (5 cores, really), the North America (AT&T and Rogers) S4 version performs just as well. Dual core versus quad core is just marketing, as there are few if any apps that take advantage of quad cores. S4 wins in some benchmarks, and the Tegra3 wins in others. But real world performance seems to be pretty much the same.
Battery life on the S4 version seems much better so far, even despite the LTE radio. And one user making side-by-side comparison (he owns both versions) says the S4 versions is flawless versus the buggy Tegra3 international version:
At this point, the only advantages I see to the international version are the increased storage, and probable better dev support.
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Phone: AT&T HTC One (M8)
Tablet: Samsung Galaxy Tab Pro 8.4 (WiFi only)