Arriving a tad later than the other two, the iPhone X has been certified by TENAA, which lists its battery and RAM capacities numbers that Apple rarely talks about. There are some good news and some bad news, neither particularly unexpected.
First the good: the X has a slightly bigger battery than the 8 Plus. Its not a huge difference, but keep in mind that the X is more compact than the Plus model. Were about to see if the AMOLED screen is more power efficient than the LCD.
The bad: you get 3GB of RAM and you better like it. Yes, the iPad Pros have 4GB of RAM and yes, they are cheaper than the iPhone X. Thats Apple for you.
Source (in Chinese)