Redmi Note 4 vs Redmi Note 4X

Updated for 2018.
In summary there are effectively 3 options to consider with the addition of the Xiaomi Redmi Note 4X (4G 64G) model.
Even though this model is classified under the Note 4X stable (released in 2017), it uses the Helio processor like the Note 4 (2016).
It therefore needs the same accessories as the Note 4 2016 model.
Quite confusing I must admit but easily applied if one knows the differences.
There are currently 2 models of the Xiaomi Redmi Note 4 in circulation but 3 different variations to consider-
 a. Redmi Note 4 ( released in late 2016 and is powered by Helio x20 processor)
 b. i) Redmi Note 4X 3G/32G ( released in early 2017 and is powered by Snapdragon 625 processor)
     ii) Redmi Note 4X 4G/64G ( released in mid 2017 and is powered by Helio X20 processor)
Here's the dilemma:
More and more vendors do not highlight this difference between the Xiaomi Redmi Note 4 and Redmi Note 4X and start calling the Note 4X just Note 4.
It's all good and well until you start to add accessories like covers and screen protectors.  
The challenge we face is that the position of the sensors at the top edge of the Note 4 and 4X models differ slightly.
Also the little LED indicator on the screen is on different sides between the two models. 
These differences impact the fit and function of screen protectors and phone covers for the Note 4 models.
Its therefore important to verify which model you have (Note 4 or Note 4x) first and select your accessories accordingly. 

How to verify

There are 2 easy ways to verify if you have a Note 4 or Note 4X

Method 1:- Phone Settings

a. Go in your Settings menu on your phone.
b. Scroll to the bottom and select "About Phone". Then look for the CPU field.
   If it says "Deca Core Max 2.11 GHZ"    >> then you have a Note 4 or Note 4X  4G/64G model
   If it says  "Octa Core Max 2.0 GHZ"     >> then you have a Note 4X 3G/32G model

Method 2:- Compare images

a. Look at the images below and compare with your phone layout.
Please note that the Note 4 layout is valid for all Helio X20 models i.e the Note4 and Note 4X 4G/64G models
THe Note 4X layout is valid for all Snapdragon models i.e. the Note 4X 3G/32G models
Xiaomi Redmi Note 4Xiaomi Redmi Note 4X
b. Confirm your model accordingly. 

Impact on Accessories

The impact is not major as both models are the same size. There is however an impact on the functioning of the screen protectors and phone covers as explained below:

1. Phone covers for the Redmi Note 4 Models 

As can be seen from the images above, the phone cover may hide some of the top edge sensors if you choose the wrong model. The biggest impact is from the position of the Infrared blaster. It will be hidden by the cover if you use the wrong model. 
The top microphone will be partially covered in case you fit the wrong model cover as there is a slight difference in position between the 2 models.

2. Screen Protectors for the Redmi Note 4 Models 

The only impact is on the LED indicator position which is different between the 2  models.
The Note 4 LED indicator is positioned on the top right of your screen and the Note 4X on the top left part of the screen.
If you choose a screen protector that is fully transparent, there is no impact on any specific model and the screen protectors can be used interchangeably.
If however you choose a "full size" screen protector, there will be an impact because this screen protector models come with an opaque frame around the edged of the protective glass.
You must therefore select the correct model if you want to use the LED indicator.
Choosing the wrong model screen protector will work in all aspects except the LED indicator will be hidden by the top opaque frame that comes with the "full screen" model screen protectors (black, white, gold, etc).

Summary

The differences between the Xiaomi Redmi Note 4 and Note 4X is quite small and may have an impact on the operation of your phone if not matched correctly to your model phone. The impacts are however not critical to the normal operation of your phone.  

You may loose some functionality in case you use the incorrect model phone case or screen protector:- 

     - the screen protector will hide the LED status indicator

     - the phone cover will partially hide the top microphone and fully cover the IR blaster. 

Please read the above description carefully and then decide for yourself if you can live with the impacts of using the incorrect accessory. Or alternatively choose the correct model accessories for your phone model.