HTC One is still the best phone I've used so far this year.
Pros: Big Screen but with a width not too wide so easy one hand use, Android customization, Amazing build quality with the Uni-Body Aluminum, one of the best screens color/resolution wise you'll see, easily side-load media without dependency to a program ie iTunes.
Cons: No MicroSD card support, No removable battery, is just getting the newest version of Android 4.3 in updates this month, Processor is one generation behind the new Snapdragon 800.
Pros: Size is easy to handle with one hand, unibody and great build quality, great screen, greater amount of apps and some would say quality with iTunes app store, pretty much guaranteed to get newest versions of OS for at least 3 life cycles, finger print reader can be used to unlock phone and make purchases from iTunes store.
Cons: No MicroSD support, no Removable Battery, locked into iTunes media one way or the other (Purchasing or using iTunes to store music to cloud/sync to phone), not very customizable, some do not like the look of iOS 7.
Pros: Screen is huge and great quality, Many custom Samsung features, easily side-load media, Micro SD Support, Removable Battery
Cons: Screen is a tad lower quality than One/iPhone 5s, some feel samsung features are gimmicks that are glitchy and take up a lot of memory, Plastic body does not appeal to some.
Pros: Newest Android version out of the box, HUGE screen, removable battery, Micro SD Card support, built in stylus, custom Samsung features, Newest Snapdragon Processor.
Cons: Size may be too big for some, plastic body, see above about samsung features.
It all comes down to what are your needs and which OS you enjoy more. Plus keep in mind if you want to be stuck to one ecosystem or the other. With Android you can easily side-load your music with drag and drop on a computer. With an iPhone you have to use iTunes or iTunes Match one way or the other.
Do you care about customization and on-screen widgets or is changing your background enough? Lots of things to consider, one thing I highly recommend is to try them all out at a Carrier Store for 10 mins or so or if you know someone with the phone.