[HTC One S] Askannon12:
Hey, i'm quite new here and tought I write here too. I have the same problem right now. Don't know which to choose. But here are some points for both phones. At first there is the One X:

It has a 720p 4.7" display, based on HTCs new Super-LCD 2 with IPS technology and NO Pentile-Matrix. It is said to be the best display out there. Bright and natural colours with very good black and white values. But as said it is a very big display and not fitted for every hand.

The body is out of polycarbonate which is quite durable but also not too hard. But it still is plastic and so it feels a bit cheap( correct me if I'm wrong). It surely feels cheaper than the HTC One S. But it's lighter :)

Let's come to the processor. The One X has the nvidia Tegra 3 Quad Core built in. It's an SoC based on the ARM Cortex A9 architecture in 40nm( for comparison: the Exynos 4210 is built on 45nm).

This isn't bad, but if you compare it to the new Krait architecture( somehow comparable to the new ARM Cortex A15 built on 28nm) it is significantly older and also slower. The Tegras GPU is an Nvidia own graphic unit which is known to be the worst of the newer GPUs( when all of them are at the same clock speed) but it should be fast enough to run most games smoothly so right now every new GPU is fast enough. A good point for the Kal-El may be the Tegra Zone, but I do not know enough of that service.

A big problem is the Quad Core unit. It's not that it's bad or doesn't work it's simply not optimized so most apps won't even fully use it. The companion core which is built into the SoC is a great power saver but it seems that it switches early to quad core( the companion core is not able to run when the quad core unit is active and the other way round) which could be seen on the battery life.

Let's come to battery life:

The One X has a 1800 mAh accu which is really good but cause of the quad core and the big display it will be consumed away very fast. So don't expect more than a day.

I don't know how much the Tegra and the display eats away so I cannot say if it will hold your 8h( display on).

I will only mention the differences of both handsets so I won't talk about the beats audio enhancement and the camera.

So let's come to the One S:

It is the smaller phone, and as you said it would be the perfect size. I think it's more comfortable to hold and also has the better feeling cause of it's unibody made out of aluminium. There are some known issues with the red black version but you can look them up in this forum.

The display is a Pentile-Matrix Super-AMOLED design with a qHD resolution( 960x540). If you compare it to the Galaxy S II Super-AMOLED-Plus non-Pentile display with a resolution of 800x480 the effective resolution is roughly the same( somehow 800*480*3 and 960*540*2 cause of the subpixel).

One problem for you may be the pixel density of the One S. When the One X has an pixel density of around 300 pixel per inch ( similar to your iPhone) the One S has one similar to your old Samsung.

The processor is something that really confuses me. It has the new Qualcomm Krait S4 SoC which seems to be a mystery.

It is built on a licensed ARMv7 architecture on 28nm called Krait. Qualcomm itself said it's comparable to a ARM Cortex A15 cpu. While that has to be seen it is clearly much faster than the Tegra 3, especially in everyday single-thread tasks. Here the Krait is extremely fast. The GPU while not the best out there is also a remarkable fast one that can compete to ARMs Mali 400 built in the Galaxy S II. You should not have problems with it.

One more thing for the Krait is it's really power efficient clocking. The Krait can clock each core independently so if it only needs one and a half :) it will clock the second core to half the speed. This gives it another great advantage over the Tegra which can only clock all together down.

At least the One S should hold as long as the One X despite it's smaller battery( 1650 mAh).

One other advantage may be the fact that some One S devices do have the new 3.0 Linux kernel. This is not confirmed but if it's right then the One S may be able to get USB-Hosting which means that you can use a real keyboard for example. This may arrive as an update.

So I personally prefer the One S despite the worse display and the small issues with the black and red version.

If you are interested in another phone you may also look for the Asus Padfone. Nearly the same stats as the One S but with an expendable storage and no beats audio enhancement. It may be interesting for you too.

Greetings Askannon