My opinion on vivo v9.
I think that vivo target those people who want iphone x look with high quality selfie camera in low price
Vivo give snapdragon 626 processor which is not a new processor . I think in this price range snapdragon 660 is also a good option
Vivo also give battery of 3200 mah but phone doesnot has fastcharging support which is also not a good option.
This phone has face unlock feature but scan only photo not scan face depth that we all can see in iphone x
So I recommended you donot buy this smartphone . This phone is only give you iphone x look or nothing