I think it is best os for laptop or pc but it also good in android it is used only for hacking
I used linux on android firstly feel it difficult but then it is awesome
This app is good for developer or hacker
The tools are awedome like nmap, sql map, aircrack-ng e.t.c
If you own any website you will need security for it that is only provided by kali linux
Fistly we have to learn about commands and uses of softwares you will get this os at sourceforge.net
So that I find it very useful