Sam Mobile put the new chip through its paces and came up with some interesting results. It scored 27617 on Antutu and 12726 on Quadrant. The reviewers said they were blown away by the results and frankly they are pretty impressive. The Exynos version seems to be a bit faster than the Snapdragon 600 version, let alone previous generation A9-based SoCs.
It should be noted that the Snapdragon 600 version seems quite competitive in its own right. In Geekbench 2 it scores 3163, ahead of the HTC One with 2687 and LG Nexus 4 with 2040 points. There's a simple explanation though, the Snapdragon 600 in the S4 is clocked at 1.9GHz, which is 200MHz more than in the HTC One. Firmware and OS differences should be taken into account as well.
Although Samsung's first big.LITTLE SoC sounds like a winner, we also need to look at the big picture. Most Galaxy S4s will be shipped with Qualcomm's LTE enabled Snapdragon 600. Samsung's quasi octa-core doesn't have LTE on board and it wasn't ready in time for the S4 launch.
In other words, it might be faster, but many consumers won't be able to get one.