2 GB RAM or 3 GB RAM, does it really matter? I am thinking to buy the new Xiaomi Redmi 3S phones that got recently launched in India. This is going to be my first Android phone. Now the phone comes with two variants, Redmi 3S with 2&nbsp;GB RAM and Redmi 3&nbsp;S prime with 3&nbsp;GB RAM, both with Qualcomm® Snapdragon 430
64-bit, octa-core processor and other specifications are identical except the prime version comes with a finger print sensor. 

I am a light user, that is, I am not going to play games or watching movies or will use lots of apps. I want the phone for general day-to-day use. 

Does it really matter to have 3&nbsp;GB RAM over 2&nbsp;GB RAM, giving my using conditions? Will it be OK with 2&nbsp;GB provided I am a light user? Does it really matter to have more RAM? Is it going to give problems with newer versions of Android?
Key aspect here light user who 


Doesn't play games
Doesn't watch movies
Doesn't use many apps
Uses only for day to day to use


If the usage pattern continues to be same for next few years. answer is no, it doesn't make a difference

While the other answer has pointed out valid instances of certain apps occupying more RAM as as time rolls, IMO it is not very pertinent given that you are not multi tasking , But if you are using RAM hoggers like Facebook which nearly takes up 0.5 GB of RAM, it may result in sluggish performance if another hungry app is opened up

How much RAM does a phone need? gives an interesting take on current trend of high RAM phones and also mentions that Google’s official minimum spec for a 64-bit phone (that’s pretty much every phone these days) is 832 MB RAM, so, you are left with one GB of RAM for apps, even if Android  OS is updated to 64 bit) and you retain your 2 GB RAM device - pretty much future proof !

Edit: Your chosen device OS is 32 bit and occupies 512 MB of RAM and if it is 64 bit  it would require 832 MB of RAM , ( as per table it is dependent on screen size and pixel density- large in your case and pixel density  is less than 300 dpi ). This size is only for the OS , radio (modem) is extra, which is not much anyway. Source : Page 56 of android Compatibility Definition

Bottom line, for your use, it shouldn't matter, since EMUI 7.0 occupies  0.5 GB and you are still left with 1.5 GB, which is plenty. Even if EMUI is upgraded, I doubt it would make a substantial difference