One thing that makes the LG G3 more attractive to me is its great line up of harware that its operating on, that I believe easily beats the other two phones in the running if the current rumors are true. To start off, their processors are all the same. What distinguishes the G3 at the offset is that it has 3GB RAM, which is one more GB than the other two contenders. It also has the best battery, 3300 mAH compared to 2600 and 2800 in the other two, meaning a significantly longer battery life, projected to be the longest-lasting battery on the market if the software isn't a big drainer.The other big thing that is going to most likely put the G3 ahead of its main competition is the actual design that you see on the outside. The screens in all three will look almost the same functionally, but the G3 is going to be much easier to deal with. By that I mean that it will be more attractive and more functional than the S5 or the One M8. The S5 has the obvious cosmetic flaw with the dimples all over its back, which gives it, in my opinion, and ugly look and the potential to gather dust. And while I have always been a fan of One's brushed metal design, I was watching a YouTube review today that said it is hard to hold onto and is a little awkward sometimes. I will be a little discouraged if the G3 also has its poer buttons on the back like the G2, although I haven't functionally used this feature so I'm not sure I'm qualified to give any opinion on it.
The second reason I think that the G3 will be the best phone out of the three competitors is its software, which historically has been better, in my opinion, than that of the other two companies. The biggest reason I've liked it is because its just normal. Samsung goes out of its way to make things seem really simple, which makes it seem to me like their phones are a lot lower end than they really are because of that special software. And with HTC, I am not a fan of their pages that show you all the social information and what not. I had a similar service with my first smartphone, the Motorola Devour, and I disabled it after about a week of having the phone because it was annoying. LG has done a nice job in the past of modifying Android like other manufacturers, but not totally butchering the flashiness of Android, like Samsung's slower page turns. LG has some cool stuff, like their lock screen that shows the weather creatively, like if its snowing snow flies down the screen, changing for each different weather condition. They add cool parts like this while still having a fast user interface.
The LG G3 will outperform the Samsung Galaxy S5 and the HTC One M8 because its hardware and its software are much better thought out. In a short disclaimer, I obviously have not used any of these phones, so this is based completely on what I've watched and read, but from what I have gathered over the last two months, this is my opinion. The LG G2 was one of my favorite phones that I did actually experience along with the One M7 and the S4, and so I predict that the unknown features of all will be similar and the G3 will again be the best phone of the year.
*No photos have been leaked of the G3 yet, so they are not included