A few days ago were the first Chromebook Cortex-A15 benchmarks with Ubuntu Linux and also then had some Exynos 5 Arndale benchmarks. I'm still working on a thorough and proper comparison of the Samsung Chromebook with its Exynos 5 Dual against other x86 and ARM parts, but for those impatient to see more numbers, I have some additional results to share this weekend.
I have uploaded a few more result files to OpenBenchmarking.org that you can find by just searching Exynos ARMv7 rev 4. In particular, 1211246-RA-EXYNOS5DU63 should be quite good if you wish to compare your own Linux system against the Samsung Chromebook as that result file contains 34 tests. With having the Phoronix Test Suite installed, simply run 1211246-RA-EXYNOS5DU63.
ChromeOS easily beats Ubuntu Linux in the overall power consumption and efficiency. Also forthcoming is another updated, big AMD Linux graphics comparison.