I was pretty surprised by some of the early benchmark tests of the SIII beating the (Tegra 3) One X. They're both basically Quad-Core Cortex-A9s clocked at 1.4GHz, but I think some of the BrowserMark differences might be software optimisations in the SIII's browser.

The One X's Tegra 3 is 40nm and the SIII's Exynos 4 is 32nm, so it should be more energy efficient. Adding more intrigue to the efficiency question is the Tegra 3's extra low-power core which if utilised properly by the OS could save even more power.

As for graphics, it looks like the Exynos 4 quad-core Mali 400/MP4 GPU is definitely faster and more powerful than the Tegra 3 GPU. It even narrowly beats the iPhone 4S' SGX543MP2 (dual-core) GPU - the previous smartphone graphics benchmark.

But, if you want mobile gaming, I would definitely get a PS Vita... The hardware in that, a quad-core A9 CPU and quad-core SGX543MP4 GPU, blows everything else away right now. The only mobile device with similar graphics horsepower is the new iPad (3) which has a very similar GPU, but has to drive a much higher res screen reducing available resources for effects.

The fact the Vita doesn't have to bother running a resource intensive OS, providing most of the available power just for games, and allows developers to code directly to the hardware also gives it an edge in efficiency.

Plus, being a gamer myself, I have to add that you just can't beat a good pair of analogue sticks and old-fashioned buttons!