Discussions about which shell is better can already be attributed to the eternal rules of God or the origin of man. But you can exhale, I'm not going to say that the shell from LG is better than all, but I just want to draw attention to its positive qualities in comparison with the stock Android. 
I will not be evaluating the design of the shell, because this is a complete subjectivity and everyone has their own favorite markers, but it must be said that outwardly the new version of the shell looks better in comparison with the previous UX 3.0, which debuted on LG G3, but about version of UX 2.0, I think there is nothing to say, it was very specific.
The new version looks more concise and modern, animations have changed, standard icons are made in the same style and have a square shape, and in general the interface has become more pleasant and, at least, looks no worse than others. But design and design are different, and the most important thing in the shells, in my opinion, is not the appearance, but additional features that expand the functionality of the device, and I want to tell you about them.
KnockOn, Knock Code
I beg your pardon if I'm wrong, but as far as I remember, the company LG was the first to implement the function of unlocking the screen by double 'tapping' in LG G2, and later many companies adopted this feature for their devices . It is very convenient when the phone is on the table and you do not need to reach for the power button, which is usually located on the right side, and in the case of LG G2, where all the control buttons were on the 'back' (as in the next flagships G3 and G4), this decision made it possible to justify the given arrangement of buttons, otherwise the user would always have to pick up the device to unlock. But the company decided to go further and created the Knock Code function. Its essence is that the screen is visually divided into four areas and with the help of a certain sequence of touches on these areas, from 2 to 8, the device is unlocked. This method of locking a smartphone is much more convenient than a pin code or pattern, but it is inferior to the fingerprint sensor in iPhone or Galaxy S6 in terms of security, convenience and speed.
Double window
Allows you to run two applications on the display at the same time, called by pressing the back button. Not everyone will find a very specific function and application to it, but personally, it often made life easier for me. For example, you can simultaneously watch a video, albeit in a small window, and carry on correspondence. Works with all applications, only some do not quite correctly adapt to half the screen. It's impossible to call it 'killer features', and Samsung has an absolutely similar function, but its presence does not interfere in any way, and some will quite like it.
Camera chips
Selfie is a very popular phenomenon nowadays. Many manufacturers use the trend and often mention in their press releases about the cool capabilities of front cameras, but the main enemy of selfie lovers is darkness. The company HTC tried to find a solution to this problem in the Desire Eye smartphone by placing the flash next to the front camera, but this is too radical a solution to the problem. In LG they did a much simpler thing and, as it seems to me, they created just an ingenious solution – the display itself is used to illuminate the face: the image from the camera is reduced, and the rest of the area is filled with white, while the screen brightness is turned to the maximum.
Another feature of the camera is QuickShot, which allows you to take a picture by pressing the volume key twice from the off state. A similar function is present on the current flagships of Samsung, only there the camera is launched by double pressing the Home button.
Smart Notice
This is a fairly simple but very handy widget that frees you from constantly viewing the weather forecast, it self-analyzes the weather data and gives a little advice, for example, 'The weather will be fine throughout the evening' or 'It will probably rain, take an umbrella'.
These four shell chips from LG, in my opinion, are very convenient and make life easier for users. For example, after the loss of Moto X, I was desperately missing the LG G2 Active Display function – the phone itself detects when you take it in your hands and activate the display, it would seem that other users live quite calmly without it, but it was hard to get out of the habit. In fact, all these are trifles, but it is these little chips that create comfort in use and are addictive, so is it useful for the manufacturer, because after the user has got used to the shell, the likelihood increases that he will buy the next version of the phone from the same company.
Thank you for attention.