Here’s a quick benchmark comparison of some popular (alpha) KitKat ROMs for the Nexus 7 2013. The benchmarks were run on AnTuTu Benchmark 4.1 on my 32 GB Nexus 7 FHD (“flo”) with stock kernels and through Dalvik (not Android Run Time). A clean wipe was done between each ROM installation.
Moral of the story – benchmarks are pretty equivocal (some Linaro magic helped SaberMOD out), and they rarely translate to “real world use.” You have a Nexus. Flash a ROM, test drive it, and then switch if you’re not happy. 🙂