Because Exynos 4 Quad has dual channel memory and a better GPU than Tegra 3?
But don't worry too much about benchmarks, especially not AnTuTu! They don't really relate all that well to actually using the device.
LG Mako - AOKP PUB/STS Kernel | Asus Grouper - AOKP PUB/Faux Kernel | HTC Vision - Flinny CM10.1 | Barnes & Noble Ovation - CarbonROM
HTC EndeavorU (eMMC Corruption Brick) | Motorola Olympus (Cooked itself) | HTC Bravo (Sold) | HTC Dream (Retired) | Apple iPhone 2G (Retired as a music player) | HTC Hermes (LCD Died)
Free RAM is wasted RAM, foo!