Android.
I've had an iPhone 4s and the Samsung Galaxy 2 and recently upgraded to the Samsung Galaxy S5.
I prefer the battery life. I go to concerts a lot and my iPhone 4s would die in my pocket. If I turn on battery saving on my S5 it lasts for days. It's perfect for traveling or when I forget to charge my phone in the morning.
The only thing I miss about my iPhone is iMessage and using iTunes for file transfers. I feel like the Android file transfer system is a little eh, but it's fully customizable and my device is rooted so I can't complain I suppose. Just a little tick of mine.