Early GLBenchmark 2.5 results put Nvidia's Tegra 4 behind both the quad-core PowerVR GPU in the Apple A6X and the Mali-T604 in the dual-core Samsung Exynos 5250.
http://www.notebookcheck.net/Popular-benchmark-claims-Tegra-4-is-slower-than-both-the-iPad-4-and-Nexus-10.87217.0.html