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 D802 - SlimKat | Asus Grouper - SlimKat-F2FS | Samsung i9100P - SlimKat/Dorimanx | HTC Vision - Flinny CM11
LG Mako (Given away!) | HTC EndeavorU (eMMC Corruption Brick) | Barnes & Noble Ovation - (LCD Stopped working) | Motorola Olympus (Cooked itself) | HTC Bravo (Sold) | HTC Dream (Retired) | Apple iPhone 2G (Retired as a music player) | HTC Hermes (Touchscreen dead)
Free RAM is wasted RAM, foo!