I got my wife the S5 for "free" when I bought my m8.
While the camera on the S5 can be good with 16MP, it also makes you hold the damn phone for like 5 seconds to take the picture. Its so annoying. If you were trying to hurry and take a quick snap of something, you wouldn't stand a chance. You hit the shutter button and it seriously says something like "hold steady..." I can't remember exactly, but it take forever to snap the picture.
My m8 on the other hand, is damn instant. Sometimes I feel like I didn't even touch the shutter button yet lol.
People always get locked on the Mega Pixels. Mega Pixels does not mean better camera/pictures. I am a photographer by hobby, and any real photographer will also tell you this. Yes its true, the more mega pixels, the clearer the image usually is when you zoom in to details. (at least on a phone that is) on a real camera, a quality lens can also make or break.
My point here is, I have a 12MP Cannon DSLR that is quite a few years old now. But I have a lot of equipment (lenses, filters, etc), and even though its only 12MP it will still make any phone camera, and also most any point-and-shoot digital camera look bad. Case-in-point = Mega Pixels doesn't mean better pictures. It means bigger pictures and larger possible print sizes. Phone manufactures know that most people think "more MP=better", and they use that to market their device to attempt to sell more (Hence all the 16MP, 20mp and even 40mp phone cameras. They know people will literally say "ohhhh more mega pixels, that will take amazing photos". Lets face it, 99% of the users are NOT going to be making large 30" photo prints with their phone pictures. So IT DOESN'T MATTER.