After the disappointing Nexus 5X release, I'm looking at either getting the LG G4 or Moto X so I've been scanning these two forums.
I've been a Moto fan so I've used the two previous X. I didn't want the Nexus 6P for it's size, and the Moto X is even bigger. G4 is big too, but there is a limit, when the length of the phone is too much it's very uncomfortable to carry it in the pocket. My past experience means I know Motorola devices never takes good photo in low light situation, and I really want a good camera this time. They also tend to lack optical image stabilization.
There are many positives with Moto X. You get a near stock Android interface which is very fast. From my experience, Motorola phones have the fastest LTE speed, best signal and voice call. I also think they make some of the most durable phones with water resistant, after opening the Moto X 2014 to replace the battery and seeing the sturdy internal design. I think Moto X phones are good choice to get if you want a reliable phones with no frills or flashy things, but just work with minimal software bugs because it's stock Android without the bloats.
For the G4, the impression I've been getting is some people is dealing with bugs like performance or battery drain issue stemming from LG software, I don't think it will effect as much. I've had the LG G2 and LG G Pad, while their software UI is a bit heavy, I find it much more usuable than Samsung, you have more choice on customizing it, Samsung won't let you disable many apps. I like the fact that LG uses onscreen navigation button, which is customizable, instead of the outdated Samsung physical button. It's not the cleanest UI, but certainly usable after you install a third party launcher and disable some of the preloaded apps.
Other things it lacks, fingerprint scanner, but is a non issue for me. Android have the Smart Lock feature, and you can double tap to wake LG phones. Dual front speakers is something I desired, but I heard the G4 rear speaker is pretty loud this time.
I'm learning more toward the G4 this time because it seems to have one of the best camera and the offer the most features overall compared to other 2015 flagships. I appreciate they offer features that most manufacturers no longer do, so you're getting good value for the money, like IR Blaster, removable battery, microSD slot, FM, 4K SlimPort (most phones now have no physical way to output to HDMI), and optional wireless charging. LG phones tend to lose it's selling value quick, but it does help make it more affordable.