Both the phones have their pros and cons, I think you should go for Galaxy C9 Pro. Galaxy C9 Pro has the following advantages over Galaxy A9 Pro.
It is not like that it is a one sided game, Galaxy A9 Pro also has the following advantages -
Verdict:- Galaxy C9 Pro has an edge over Galaxy A9 Pro but it is priced relatively higher than the Galaxy A9 Pro but considering the performance drop of Galaxy A9 Pro at a much lower price Galaxy A9 Pro also has its own charm to buy.
You can compare this on our 91mobiles link:Galaxy C9 Pro vs Galaxy A9 Pro
You can also check this video comparison
Vivo V5 Plus vs Galaxy A9 Pro
Both the phones have their pros and cons, but I think you should go for Samsung Galaxy A9 Pro.
Samsung Galaxy A9 Pro has the following advantages over Vivo V5 Plus:-
1.Samsung Galaxy A9 Pro has 6.0" Display Size while Vivo V5 Plus has 5.5" Display Size.
2.Samsung Galaxy A9 Pro has 5000mAh Battery while Vivo V5 Plus has 3055mAh Battery.
Vivo V5 Plus has the following Advantages also:-
1. Vivo V5 Plus has 64GB storage capacity while Samsung Galaxy A9 Pro has 32GB storage.
2. Vivo V5 Plus has 20MP Front camera while Samsung Galaxy A9 Pro has 8MP Front Camera.
Verdict- In my opinion, Samsung Galaxy A9 Pro is a better phone in overall performance but if you need a phone with a good camera you can go for Vivo V5 Plus.
you can also see the comparison between the devices on 91mobiles: Vivo V5 Plus vs Galaxy A9 Pro