port80 wroteLG G3: LG doesn't know how to make phones their version of android is pure sh*t. I got a G2 after my S4 was stolen and it ws the worst phone I ever had and am currently stuck with. It took a lot of rooting and installing roms to make it remotely close to the S4.
Z2: Add sony to LG not really good at making phones let them stick to something else.
OneM8: Looks good online. Isn't really in real life. Basically like the iphone, just a flashy phone that is not worth the price.
S5: As I said I had an S4 and it was great. Samsung is a great phone manufacturer and I have no complaints about it. The S5 is even better and I recommend it.
That's the most biased and ignorant reply I've ever seen. The original poster asked for advice based on specifications, not your own personal opinion.
First of all Ramii, you have to find out what you're looking for. If it's battery life, you can go for the Sony Xperia Z2. With its 3200mAh battery, it should give you a day and a half with heavy usage. The problem with Sony phones is that their updates are known to be very slow, and it can take months to reach certain regions.
HTC M8 has a really good design, but worst battery life of all at 2600mAh. The HTC interface Zoe and Blinkfeed is also not for everyone's taste, so make sure to check it on YouTube for a full tour of the phone.
Samsung Galaxy S5 is for you if you like the TouchWiz launcher and don't mind the design on the back that looks like a band-aid. It has a battery life of 2800mAh and has the best customer service with more updates than the rest.
Then you've got the LG G3. Out of all the rest, it has the best screen, with a 5.5" QHD screen with a resolution of 1440 x 2560. The screen size rivals that of the Galaxy Note 3 while retaining a smaller phone dimensions overall. Even though this is the most beautiful and innovative phone out of the four, it also has the most issues. Its Snapdragon 801 chipset isn't designed to handle a 2k display, which often results in overheating. Second, this phone battery houses only 3000mAh, which is a problem when you have a QHD screen. It will suck the life out of the battery easily due to the high resolution.
All four phones have similar specs, each one housing the Snapdragon 801 chipset, with HTC M8 and Galaxy S5 having 2GB RAM, and the rest having 3GB RAM.
Now to the really important part: This September there will be announcements for new phones by Samsung (Galaxy Note 4), Sony (Xperia Z3 and Z3 Compact), Motorola (Possibly Motorola X+1 and Moto 360 smartwatch), Apple (iPhone 6), and in the months after a possible Nexus 6 announcement (also by Motorola). The Galaxy Note 4 and the Nexus 6 will most probably have a Snapdragon 805 chip, which offers much better thermal and battery management, while also rumored to have the same QHD screens as the LG G3.
Even better yet, if you can wait until Q1 of next year, the smartphones will start to come out with the new ARMv8 processor that houses 64-bit chipsets, a key element in the next Android L. These chipsets will bring huge improvements to all aspects of smartphones compared to the ones we have now, which all house the ARMv7 processor. Check the Qualcomm webpage for more details. I hope this helped.