Which Antivirus to purchase?

If you need to spend some money then you should definitely go for Kaspersky but there is an alternative.
As you are on Windows 10 then you can just simply stay with built-in security tools (Windows Defender and Firewall) and just add VoodooShield (free is enough) and some on demand scanner - HitmanPro (paid), Zemana Anti-Malware free, Emsisoft Emergency Kit.
 
This antivirus software on the picture looks quite old. Just compare the cover of Bitdefender today and the cover on the picture. Fresh meat tastes better than old meat and so it is here: Old AV software contains poorer support than new ones.
Whatever. You use Bitdefender and like it then stay with it. You don't like Bitdefender, then try a trial version of Norton. If you have such offers (trials), you should also use them.
 
Both of them have 30 day trial versions so why not trying them first and choose whatever suits you the best?
I agree. You should never buy an antivirus without first testing it on the computer you are going to use it on. That way you can see if it causes any slowdowns or other issues with your computer. The performance impact of security software can vary so much from one computer to next, you need to test it on the computer you will be using it to see how it works for you. What is light for someone else, may make your system run a lot slower.
 
Both of them have 30 day trial versions so why not trying them first and choose whatever suits you the best?
+1. This is the way to go. Try the trial and see what works the best for you. All those products provide great protection but usability depends upon your system, what works for others may not work well for you.
 
Bitdefender or Kaspersky???
This antivirus software on the picture looks quite old
@low L!fe where are you from? India
I suggest you never go with an older version of Bitdefender because this license is sold by the third party. They will never give you upgrade to newer versions. Purchase 2017 version only.