Samsung is a big and important company in the mobile space right now, but their devices are not without criticism, nor are they the be-all and end-all of smartphones. Depending on what it brings to the table, people may or may not prefer it over the HTC One, or other devices. So what are the things the Galaxy S4 needs to beat HTC One, and make people hold off from buying a HTC One?
This is an easy one to spot, and it's an easy one for Samsung to use against HTC, considering they are launching the device later than HTC, and their negotiation power in getting parts. So far Samsung has tried to have the fastest phone on the market, and they haven't disappointed in this area, yet. I expect their chip, whether an overclocked S600 or an Exynos 5 Octa, to beat HTC One's chip.
We already know that the resolution of the Galaxy S4 is going to be 1080p, just like HTC One, although with slightly fewer pixels per inch, but the perceptible difference between 440 PPI and 480 PPI shouldn't really exist, or most people won't notice it. What will make the difference here is the quality of the panel itself.
Samsung is rumored to drop the Super AMOLED panel from Galaxy S4, which would be a first in the life of Galaxy S flagship. But I think that's a good thing for them. It will be easier and cheaper to manufacture a 1080p 5" panel. And let's not forget Samsung is one of the best display makers out there. What will really make the difference is having a very high contrast IPS/PLS panel (say 2000:1 or so) and 100% color accuracy.
I think in the coming years having the better camera will be more important than having the better processor. We should see a resurgence of the camera competition that we saw in the early 2000's before the iPhone appeared. One of the ways to have a better camera by leaps and bounds will be to stop competing with the same size sensor as everyone else and keep increasing megapixel count.
The two best ways to compete in camera performance in the future will be to either use pixel binning/oversampling or increase the size of the pixels. Both ways will need as large sensors as possible to do that properly. HTC One has barely scratched the surface with the HTC One camera, because they only lowered the MP count, but kept the sensor size the same. Unfortunately, it doesn't look like the Galaxy S4 camera will do any of these.
I also think all smartphone cameras should come with Optical Image Stabilization, and it's possible Galaxy S4 won't have it, which would be quite a disappointment, as I think OIS is a very needed feature for smartphone cameras to save us from shaky pictures and videos.
Better design and build quality
These two go hand in hand. A good polished design can also improve how good the device feels in hand. HTC One got a lot right here, with great design and solid aluminum casing. Can the Galaxy S4 top this? Probably not, and again an unfortunate thing. I will not accept Samsung's excuse that plastic helps them cut costs and it's easier to use. I'm not debating if that is true or not. I'm sure it is. I'm just debating it from the point of view of why would that be a factor in a $700 device? Because it shouldn't be. If I'm going to pay $700 for a device, I kind of expect to have it built from a material that cost them more than $10.
New Innovative Features
This is always needed to differentiate yourself from the competition. Unfortunately, most companies don't do this enough, and they usually just think about how to copy other companies' features, instead of thinking about what new features they can introduce to wow their customers. But when they do think about this, a lot of the time they just end up adding useless gimmicks, that add to the cost of the device, but don't really improve it.
If Samsung can get a lot of these right, then the Galaxy S4 will be a no-brainer. If not, then the choice will be harder, at least if people compare the 2 devices rationally, and don't just buy them because a lot of their friends have it.