HTC and Sony both know how to make flagship devices with great looks and premium feel. The two companies took different approaches to the design, but the final result was great in both cases.
HTC has stuck to its guns, building a gapless unibody smartphone that is entirely made out of high-grade aluminum and feels impressively solid in the hand. The only part of the One that comes off is the SIM tray but even that requires a tool to operate.
Sony has put their best design ideas behind the Xperia Z and labeled it as precision engineered. The front and back panels of the smartphone are made out of tempered scratch-resistant glass that look stunning, even if they are not quite as solid when held in hand. The company also paid proper attention to details like the signature power button, which is specifically engineered for comfortable operation. The Xperia Z isn't a unibody construction but doesn't have a removable back cover, so accessing the battery is, again, a no-go.
That said, the Sony Xperia Z design still holds a few important advantages over the HTC One unibody. The IP57 certification for water and dust resistance is the most prominent among those, but you shouldn't also forget the microSD card slot that allows for cheap and quick memory expansion. There's also the microSIM slot which can be operated without a sharp tool at hand, which might come in handy if you need to swap SIM cards on the go.
The HTC One has gone with a slightly smaller 4.7" screen, allowing it to retain a slightly slimmer footpint despite the dual-frontal speakers, each with its own Beats amplifier. The marketing term here is BoomSound and the benefits are easy to hear. The HTC One offers clearer and deeper sound than any device we've ever heard in the office and the placement of the speakers means watching videos or playing games will be a more immersive experience.
The Sony Xperia Z strikes back with a super slim 7.9mm waistline, which means it have a smaller overall volume despite its larger 5" screen. Of course, you should keep in mind that the Xperia Z's screen features on-screen buttons that take away from the real estate, but the software hides them in the gallery and video player, and while playing games so you get the extra space back where it counts.
The HTC One isn't in the running for thinnest device but manages an acceptable 9.3 mm waistline. Its hardware controls do cause some usability issues though. The power button (which doubles as an IR emitter for controlling various appliances around your home) is located on top and is a rather hard to reach. The key itself is sitting pretty low and its press feedback is poor - traits shared with the volume rocker on the right side of the HTC One.
The sides of the smartphone have nice colored accents and feel almost unanimous to the finger until you open the flaps over the SIM, microUSB or microSD card slots, which are all covered with plastic flaps in order to fend of water and dusts.
The volume rocker consists of a thin and long button, while the power button is raised and falls comfortably under your thumb. Both buttons feel responsive and refined with good elevation and are fine-tuned to give out the right feedback.
Due to its sharp edges the Xperia Z feels very broad and is a bit unwieldy for those with small hands.
On the back of both devices you'll find the camera lenses complete with single LED flashes and secondary, noise-suppressing microphones. The HTC One has an arching design, which starts off slim at the extremes and grows thicker towards the center of the back. The Xperia Z relies on the same philosophy as on the front - flat minimal surface.
Winner: Sony Xperia Z. While we prefer the looks and the feel of the HTC One, the practical advantages of the Sony Xperia Z earn it the victory here. The IP57 certification, the microSD card slot, the easily swappable SIM slot and the more comfortable buttons outweigh the benefits of the aluminum unibody.