I agree with swtrainer.
I did a bunch of research and then went to the VZW store. I've loved Samsung phones but (and was moving from a Note 3) but I absolutely could not stand or justify the S6. Didn't like the ergonomics, didn't like the smaller screen,didn't like the style. Some of these issues can be dealt with using a case. But here's where I feel Samsung lost the soul of their Galaxy line...they took away my freedom and choice by removing the microSD card slot and the removable battery. I agree that the battery is less of an issue than it used to be with battery cases, external battery packs, etc. But,eventually,that battery will lose its ability hold a charge and literally for a few bucks, I'll have a new one. The microSD is just great. I love taking full advantage of the camera and video capabilities and I never have to worry about how much I'm shooting and I don't have to rely on my data plan to upload stuff so I can take more photos/video. Maybe not important to some people but I love it. Also great for caching online radio for streaming without using data or worrying about signal strength on long trips. Also great for the same thing with movies. Plus you can now save YouTube videos if you have Google Play Music/YouTube Red. Expansion card slots just give a lot of flexibility that I'm not willing to give up.
The camera depends on what you want to some extent. The LG G4 camera is absolutely fantastic. Like love, love, love, adore it. The low light performance is unmatched by any other camera I've used and you can easily capture shots without a flash that would be impossible with my Note 3, or even my good bridge camera. Fill manual control if you want it, excellent auto performance if you don't. It's seriously a photo lover's dream camera for a smartphone. I'm also a huge fan and convert to the rear buttons. Wasn't sure at first if I'd get onto the feel of it but after just a few hours,it's so much more natural than anything else. Can be used with either hand and doesn't accidentally turn on or off when changing orientation and the like which happened often on my previous phones. I'm also a huge fan and convert to the on screen buttons. My husband's Samsung Galaxy phone had the home button completely die and in order to fix it requires replacing not only the entire screen but multiple other pieces and cost several hundred dollars. Can't happen with on screen buttons and I love that they change basin on screen orientation and context.
I love the screen and design of the G4. Easy to hold on the hand and yet almost the same size as my Note 3.
The other thing I couldn't justify was the price difference. In addition to all the ergonomics, design, battery, expansion card slot, camera, UI, etc, I simply couldn't justify the price difference. Im not sure what they current pricing is but it was going to cost us $250 more for the S6 with half the memory of the G4. That sealed the decision for me. Samsung I had heard was forced to drop prices around the time we purchased but it might be closer now. If I had adored the S6 maybe it would have been worth it. But no way. I was honestly really sad and disappointed to see the new Samsung line. I loved, loved my previous Samsung phones...but not the new ones. :-(
I just have to add that I haven't had any issues with my battery like one previous poster mentioned. I almost never run out of battery before the end of day. I don't use a battery saver, turn things off, or anything else like that. And I quick charge technology, which I believe the CD has as well. Makes a huge difference for me knowing that if battery does run low sometime, just 30 min gets me to 60-70% charge. IMy husband also has the G4 and often will only charge his phone every other night.
Phones are super personal and you'll have to decide what's most important to you. I was looking for a new phone now, I'd also have the LG V10 on my list as others have mentioned and I'd likely be choosing between the G4 and V10. But the differences will depend on your needs, wants, and use. Good luck with your decision.