According to Antutu, the benchmarks of both devices are pretty similar.If you're there for the pure Android experience or having the rom-switching pleasure, then do Nexus 5. Otherwise, from my limited time with both phones, I would say go for the ZF2 for its larger RAM, better camera, and newer processor (though not necessarily/noticeably faster). I don't have a strong memory regarding N5's battery life - but just here to say that though some reviews suggested otherwise, ZF2 has wonderful battery life. My ZF2 always last more than a day even under heavy usage.