Make no mistake, for while you may have gone through the soul-searching exercise that is deciding which flagship to go for, a whole lot of other people are about to be faced with the same.
Aesthetics have, are, and will continue to be susceptible to the ever-changing whims of each individual person's taste, but that doesn't mean no considerations are based in fact. When faced with each other, there's actually a pretty stark difference between the Xperia Z1S and the Galaxy S4. The former undeniably features the sturdier, more premium (and edgy) build, with its all-glass back and metal frame. Samsung's rounded polycarbonate construction may well leave something to desire, but the phone is not to be underestimated, as it's both considerably more compact and perceptibly lighter (6oz vs 4.59oz). So, as far as design matters are concerned, it really does come down to a simple choice between a premium design or compactness.
Things are considerably more clear-cut when it comes down to the display panels on the Xperia Z1S and the Galaxy S4. Both feature a 5-inch, 1080p screens, though the tech behind them does differ quite a bit. As much of an improvement as the Z1S' Triluminos TFT LCD display is over its predecessor's, it's still not perfect (i.e., still pretty poor viewing angles). On the other hand, the Z1S' screen is considerably more accurate with its colors, producing more life-like images, whereas the Galaxy S4's AMOLED panel is sometimes completely off mark. That being said, the S4 does offer some seriously saturated colors, next to which, the Z1S' look downright washed out. It's easy to see, then, why, to the untrained eyes, the Galaxy S4's screen looks miles ahead of the Z1S'. What's more, some people knowingly prefer those over-saturated, festive colors, to the those that resemble everyday reality.
The Xperia Z1S' interface appears quite different next to the one on Samsung's Galaxy S4. The Japanese company has opted for much more subtle changes, and elements are generally in darker colors. Sony's UI is functional, but not overboard, striking a pleasant mix.
Samsung, however, has gone down a much different path. Its TouchWiz UI is a full-blown replacement of Android, and it tries to be just about everything. Bright, over-saturated colors are more common throughout, and functionality has simplicity's head on a spike long ago. This is still down to taste, but we've often found ourselves questioning Samsung's feverish attempts to cover all bases. All this extra eye-candy and functionality has a cost attached to it, and that's performance, at least on occasion. In comparison, the Z1S' UI runs buttery smooth, though that's not an entirely fair comparison, considering the...
Processor and memory
That's right, the one aspect in which Sony has a definite edge over Samsung is its chipset, seeing as the amount of RAM is equal, at 2GB. Equipped with a 2.2GHz, quad-core Snapdragon 800, the Z1S is on the receiving end of more power, for less. It easily handles just about any one task you can think of it, including the heaviest crop of 3D games. Browsing is fast and buttery smooth, without any hiccups whatsoever.
So, is the Samsung Galaxy S4 totally outclassed here? Not exactly. Packing a none-too-shabby 1.7GHz, quad-core Snapdragon 600 from Qualcomm, the S4 is no punk, either. There is some slowing down every now and then, but we attribute this more to Samsung's heavier skin, more so than an actually perceptible difference between the two. In conclusion, the chip on Sony's flagship is a bit more forward-looking, but it would be ridiculous to sell the S4 short, based on performance alone.
The Sony Xperia Z1S definitely takes the crown in the camera department, so long as pixel count is all that matters to you. Its 20.7-megapixel camera unit with G-lens and an Exmor RS sensor sounds downright impressive next to Samsung's 13-megapixel one, yet, in reality, the difference sure isn't as clear cut. In other words, while we've consistently found Sony's results to pull ahead of the S4's, there are some important things to pay attention to.
For starters, the higher pixel count does make a difference, and given optimal conditions, the Z1S undeniably captures more detail than the S4. Unfortunately, when the lights go down, we've often found the Z1S' resulting shots to be almost insignificantly better than ones from the S4.