The finger print lock is only going to protect your data on the phone, as soon as a thief has the phone he will just DFU restore it.
But iPhone 5S will ship with iOS 7, so if you turn on Find My iPhone, even a DFU restore won't work. The thief will get a message saying they need to enter the password of the Apple ID the phone is associated with, and since they don't know that password, the phone would just be a paperweight.