If you want something plain and simple, then go for the iPhone 5s. But if you want to be techy and want to customize a lot of things, the HTC One is the better choice. However, since you are already using a 4s, upgrading to a 5s will be very easy as everything is backed up by itunes.
So, to sum it up, think about it like this:
iPhone 5s - Same great thing.
HTC One - New adventures.