I must admit, the only thing at the moment that would be drawing me towards the M8 is the front speakers. But logically thinking if I want to listen to something properly I'll just stick a decent set of ear phones in.
Build quality doesn't bother me at all, I'm only gonna put a case on what ever phone I have.
As mentioned above, those on screen buttons don't sound good.
I'm really happy choosing the S5, but hearing a bit of hype of the M8 so was wondering if I missed something and chose the wrong phone???
I also have about a week to change my mind just case
Honestly depends on what you are looking for in a device. Like I said, the s5's camera is what mainly made me want the s5. But the hindrance of memory and hardware/software that bogged it down is what made me want to return it. As far as the m8 goes....
Music/audio sounds ridiculously good on the m8. And I'm talking about with headphones.
Memory. It comes with twice the available memory over the s5 for the same price. So if you plan on storing a lot of memory intensive apps.....
It's actually faster and more fluid than the s5, despite that the s5 is clocked faster. Screen rotation, going through apps, web pages...it's only by like a second, but it's still faster.
The on screen buttons really are not that much of a hindrance like people are making it out to be. If you are texting or whatever, they aren't going to bother you since you are already typing away anyway. If you are watching a movie or playing a game, they go away until you swipe the area of the screen where they would be. Like I said, they really are not a bother at all.
Battery. You can switch out with the s5 (which is a good thing if you are a mega heavy power user), but if you always recharge your phone at the end of the day, then both of these devices will carry you through, especially since both of these devices come with ultra power saving mode.
Even texting is better on the m8. It may not have the number row like the s5 does (which is a good thing), but the predictive text works so much better to the point where it's almost reminiscent of the iPhone in terms of texting.
Basically it's the little things that make the experience. Both phones are in fact great. But everyone's needs and what they want from a phone is completely different. Think about what you want exactly out of a phone, then think about what each phone brings. Match the phones price and the hardware/software capabilities that come with that price with your needs and then go from there, because it is your money that you are investing in