[AT&T Samsung Galaxy S 5] 903tex:
Here my review as I've had both devices in the past couples of days.

Design m8> s5

Both phones to me look great but the design on the m8 is sexy! When I saw the s5 all I've seen where white models, which to me made the phone look horrible cause of the added width made the screen look smaller than it actually is UNTIL I got my black s5 and loved it as soon as I traded my m8 in.

Camera s5> m8

Pics on the m8 ON THE PHONE look amazing but when crop you see the flaw in the 4mp shooter. S5 camera just clearly is the better point shoot camera if you want to use your pics past social media uploads. If not then M8 should do you fine.

One hand use s5> m8

As sexy as the m8 is the back is slippery and I felt very uncomfortable one hand using the phone and the fact that the m8 is narrow and taller reaching the top of the screen was a scary thing to do as I was running the phone with no case whatsoever. Case Will solve the slippery back but with the s5 I don't feel like I need a case as the back is nice to touch and being that the phone is lighter than the m8 makes me feel I have one hand control of the phone at all time.

Speakers m8> s5

Don't really need to go into this and one of the features I miss on the m8 as I do listen to a lot of music.

Screen draw

Both are beautiful

Features s5> m8

S5 more featured packed but the features in the m8 are no slouch

Wish the s5 had the double tap to wake the phone but since it has the finger print I can see why they didn't go with that feature. Overall while some think their gimmicky the features on the s5 are fun and very useful to use when need be.

Internal memory m8> s5

More internal storage for the same price as a 16gb s5 is always gonna be better for some. NOW the SD card slot is working great for me so my Internal memory can be just for apps but those that don't like SD then note the s5 32gb will be slightly more on contract and off contract than the m8.

Battery life s5 > m8

My s5 is doing great and I love the feature with the power saving option offering a extended mode for those needs when Your at 10% and won't be near a charger for period of time.

But the m8 battery life is just as good as the s5 with my units I had.

Custom Roms m8> s5

One of the big reason xda was started for and unless u have the t-mobile variant then root and maybe a stock tw rom is all your gonna get from the s5 att model. But the experience with the new tw is very nice and I'm not seeing lag as previous galaxy phones in the past

So basically it comes down to this

Features or custom roms?

Top build quality or water resistant plastic?

4mp or 16mp camera?

Boomsound or fingerprint?

I don't think you can go wrong with any of the two flagships. Custom roms are great but some don't function and leave features that sold you into the phone from the beginning. Samsung is becoming apple which is not a bad thing. I remember when HTC was doing the locked bl and fans went nuts then they slowly changed their ways of tactics. as a phone the s5 and the m8 IS that plus some. now I'm more than happy with my s5, you may need your root and that's it which I see s5 having at some point very soon. But if u need your custom kernels and aosp roms then don't even look at the s5. Hope this helps those deciding between the two....