some note for u. stock android is not for everyone if u r not familiar with it. some might feel hassle to install other apps (i.e file manager, app lock, call recorder etc..) 

if u want value for money good battery life i definitely recommend u to get the lenovo p2. (the battery, screen, speaker is damn awesome)

I'm not saying Mi A1 not good it's just I feel something is missing from my point of view. Overall mi a1 is good phone.

Better with mi A1, supported up to android P at least.

generally it's all about efficiency/optimization. faster doesn't means it will always perform better (tendency getting hot real quick, battery life.. etc)
than just forget about mi product. stick with your most trusted/reliable brand