Nexus 5 or hold on to my iPhone 5?

I currently own an iPhone 5 16 GB but I'm really tempted to get a nexus 5 because of the the new ART tech and android L. I can easily sell my iphone and get enough money for a 32 gb nexus 5, but I'm confused. My main requirements are best performance and super smooth lag free UI experience(which I love about my iphone right now)and battery backup. I've used android before on my old GS3, but it sucked. So please guys, I need advice from those who have used both iphone 5 and nexus 5. What should I do?

I bought an iphone 5s to replace my Nexus 5 just a week ago and it was a terrible desicion. What i'm going to say may be biased because i've been and android person all the time. In raw power, (CPU, RAM, GPU…) android phones win anytime and have multitasking but iphones are very well optimized and lag isn't a common thing either. In a few years both phones will become obsolete but the iphone 5 will probably start lagging due to some update (just like the iphone 4). On the other hand, you can install custom ROMs and stuff on your nexus 5 if the performance is bad (though it shouldn't be). Its up to you, whether you want an uncustomizable phone with low-end specs but good optimization or a customizable phone with higher end specs. I prefer the latter…

If you used it before and it sucked, then I wouldnt go that route. I would move up to iphone 6 which is going to be out in a couple weeks.

I currently own the Nexus 5. I'm not a fan of apple products but if you are happy with your iPhone 5 then why bother getting a nexus 5? Like anonymous said, if you're planning on getting a new phone, move up to the iphone 6. And if you have used android before on the Samsung Galaxy S3 (Which runs a pretty recent version of android) and didn't like it then don't bother moving into android.