[AT&T Samsung Galaxy S 4 General] BarryH_GEG:
The h/w specs are about the same. The One's got forward facing speakers, a smaller display, non-expandable storage, a fixed battery, and a different but not universally better camera. The SGS4's thinner, lighter, has a larger display, 13MP camera (the iP5s will be 12MP), bigger swappable battery, expandable storage, DDR3 memory, GG3 and 4.2. The biggest advantage for the SGS4 is customization and what its s/w can do. If that doesn't mean anything to you stick with the One. I had a One X and Sense 5 does less than Sense 4+ because HTC removed themes, scenes, and a lot of popular widgets to accommodate BlinkFeed which isn’t very customizable, can’t be disabled, and not universally loved. I'd have a real hard time going back to Sense and its lack of features.

Here's what the SGS4 can do s/w wise. If none of the below means anything to you than pick whichever phone makes you happiest.

The ability to turn off the capacitive button lights so if you're navigating or watching flash-based video in a browser they don't distract you.

Long pressing a function in the notification bar opens that function. (EG: short press Wi-Fi = toggle, long press=open Wi-Fi settings) so you have quick access to most used settings no matter where you are in the UI or an app.

Customize which functions appear in the notification bar and reorder them.

Unlock the device via voice including separate commands to unlock via voice directly in to various apps.

Use voice to control the music player, take a picture, snooze or shut off the alarm, or accept or reject an incoming call.

Launch the camera while the device is locked by holding a finger on it and rotating it from vertical to horizontal.

Smart Stay to keep the device awake when looking at it and Smart Rotation to keep it at the same orientation as your eyes if you change position.

Music Hub subscription service with locker storage (matched) for your own music and the ability to download unlimited songs (while subscribed) to the device's SD card and have them all show up in the stock music player.

Music Square which determines the "mood" of all your stored music and allows you to instantly create playlists based on the mood of a song you're currently listening to.

S Voice to control a much broader list of functions by voice than what’s supported by Google Now and dial by name or number via BT including sending MMS and e-mail.

Quick Glance to see time, date, weather, battery life, missed calls/messages, and new e-mail by waving your hand over the device without unlocking it.

Customize your e-mail signature in the stock e-mail client including different fonts, colors, and graphics.

Direct call to automatically dial a number from an open contact, MMS, or e-mail message.

Palm touch to mute the device by covering it with your hand.

Driving mode to read incoming MMS and e-mail aloud.

Airview to preview contents without having to open them (e-mail [body and sender], MMS, web links, pics, videos, and docs in folders). Airview also lets you see the detail of incoming messages (MMS, missed calls, and e-mail) by hovering over the notification on the lock screen.

Hover to control the display (up, down, across) by hovering over an edge. It also allows you to use drop down menus on websites rather than having to click multiple links to get to the page/topic you're looking for.

Multiview to look up stuff in one window to use in another or check something in somewhere else without interrupting what you're currently working on in another app.

KiesAir to send and receive MMS while the phone's docked and reject incoming calls. Also access all your content via a PC; even when using someone else’s.