@DIDIx13
WHGhost is right about your client will need a good firewall. But it should still be looked into. I haven’t played with 2016 and it might have win defender. If they want something more, you need to know
What is their price point?
What type of attacks does your client expect to have?
What is the server being used for?
How many people have access physically and virtually to the server?
Thing to note is most AV are about the same. Unless if you get an unknown no name one, they tend to all get the same definitions about at the same time. Things you need to note is can it scan for polymorphic malware, can it scan for rootkits, how the firewall works, and so on.
I have a few videos on this type of thing. You can see what polymorphic malware is here
Depending on the budget, you might want to look into net gen firewalls. My background with them is more into palo alto networks. But these basically look at the packet details vs blocking ports or whatever. An example these companies use is say if you want to block someone from playing farmville at work. To do this you will really need to block port 80 or block the website. The problem with this is blocking 80 will block most everything, and blocking FB or whatever might mess over the marketing team. So the next gen firewall will look at the packets itself and check with your rules. Some can even go as far as looking for malware (I’m not sure how good they are).