You are not mistaken, but missed one step in between, SGS 4 i9505 

Frankly speaking, I see no reason to upgrade from HTC One to Nexus 5 if your HTC One is working perfectly, e.g. no camera purple tint.

The Nexus 5 is the fastest among the three (HTC One, SGS 4), but out of the three, SGS 4 was the slowest and by a big margin. Slow as in response time, the fluidness/smoothness of just swiping the screen. EDIT: Too much Samsung bloatware.

Out of the box, HTC One has the best package, in terms of Blinkfeed, and simple things like a button build into Sense to turn on the LED as a flashlight.

For the Nexus 5, it is a Google device, plain vanilla and you can do literally whatever you want with it.

So it depends what YOU use it for. If you like to tinker a lot, and customize stuff to your unique liking, Nexus 5 hands down. If you're lazy, not bothered and you just want something as a whole package, its the HTC One.

As for ergonomics, HTC One wins hands down. For 1 handed operation, the Nexus 5 works, but the HTC One works even better with its smaller screen - easier to grip and use with 1 hand, and the buttons below. On Nexus 5, the buttons take up the space on the screen. Zzz.

Nexus 5 is nice finish, but HTC One is much nicer. And the HTC One feels more of a premium device.

Why am I using a Nexus 5? Because HTC One is faulty, i cannot stand paying RM1.9k for a top end device that has a faulty camera that is unable to take pictures properly. Otherwise I'd still be using HTC One today.