A lot depends on what you are looking for.
I use an iPhone 5 - basically because the OS and app store are far more secure than Android and the android store. However, the price I pay for that is less customisability and and sometimes a loss of features. You'll get fanboys on both sides and there will always end up being a huge argument but in a nutshell, for me it's security and privacy VS customisability.
The difference between the 5c and 5s iphones? The 5c is basically a repackaged iPhone5. The 5s is a 64bit device. At the moment there isn't a lot of difference in performance, but there will be when apps are coded for 64bit native rather than 32bit. The 5s also has a faily cool fingerprint scanner, which gives a bit more security too. But the fingerprint scanner isn't unique to iPhones.
I develop apps for both android and iOS. I like iOS better subjectively, and also appreciate the lesser security concerns (although it's still by no means completely secure). I use an iPhone 5, and Nexus 4 and an older cheapo android device. The Nexus is a nice device, the iPhone is a great device. The cheapo is OK.
I guess it depends on what you're looking for, but for, as said before, me it came down to security vs features. the iPhone won by a margin.
Check out reviews from places like The Register and you'll get a decent objective review.