[LG G6 Questions and Answers] HanMan5000:
I can help with this!

I was using the S8 (USA version) from late May until about 2 days ago and I've also been in Spain since late May for work. Unfortunately I broke the **** out of my S8 (it scratches, cracks, and or breaks extremely easily without a case) and while I have the Samsung insurance, they don't ship outside of the USA apparently.

Since i'd be in be in Europe for a few more weeks, I decided to pick up the G6 since it was way cheaper than the S8 (at least in Barcelona). I was surprised to see how much more I liked this phone than the S8, I would have never seen myself as getting a LG phone but it was the only other phone with a high display ratio like the S8.. and after I used the high display ratio on the S8 I just couldn't go back (even temporarily).

Anyway, let's talk about the good stuff.

-Display/Design: I like the S8's design a little better (narrower and easily to hold, curved screen looks cooler). LG Display is still great though. As for the design, the metal sides on the G6 feel much better. I also like how the fingerprint scanner is placed on the G6 but moreso how it's also a power button. I don't like how the G6 has the headphone jack on the top, though, but I'm glad it's at least there.

-Software: The S8 was so slow. Even going through Package Disabler and disabling a good amount of the bloatware (and using Nova Launcher Prime) the thing lagged way too much. This drove me nuts. I tried optimizing it as best I could. I got it a little better, but still nowhere near as fluid as I thought such an expensive flagship would be. On the G6 the software is so much quicker. There's much less added bloatware (don't get me wrong, some of the bloatware on the S8 is actually really nice) and everything is much more fluid. It's extremely close to stock Android. On the S8 you click the home button and there's sometimes a delay; I haven't really noticed this with the G6.

-Camera: I took some jaw dropping photos with my S8 -- haven't had much time to try the G6's yet but hopefully it's as good. G6 has dual cameras and wide angle options on the front and back, so there's that.

-Battery: Too early for me to make a judgement on this but I wasn't really happy with the battery I was getting on the S8 (with optimizations). Fast charge is nice and on both.

-SideSync: SideSync is a Samsung only feature that lets you control AND mirror your entire Android device and get all of its notifications on the PC. I was blown the **** away at how well Samsung developed this (it wasn't half assed like some Samsung stuff is). It worked very well connected via both Wifi and USB. It actually saved my life when my LCD died by enabling me to use every aspect of my phone.

-Iris Scanner: It worked really well, but its not practical. You have to hold the phone up and angle it a certain way EVERY TIME you try to unlock using it. It's stupid.

-Fingerprint Scanner: Both devices have really good ones. I think the G6's is slightly better but I could just be perceiving this because it's easier to put your finger on and its bigger).

-Heartbeat sensor: S8 has one, works pretty well (not sure about accuracy but seems accurate). Can't say I really used it much.

My deciding factor on why I prefer the G6 is the software. There's a lot of negative attention on the fingerprint scanner but not so much on how slow the software was. I expect a flagship to have minimal stutter and be pretty fluid. The S8 was a huge disappointment when it came to that despite the several optimizations I made. The S8 has a killer design, great hardware, and some great features (like SideSync), but the software lag is a deal breaker.

Note: I was using a US variant of the S8 with the ****tier processor, but personally I don't believe that the processor difference would be big enough to make it as slow as it was.