Hi, I've used Kaspersky on a number of devices for the last 3 years and I have never really noticed it being in the background and doinf it's stuff. It has done it's job by blocking malware etc.
In December, Kaspersky license ran out and a friend recommended BitDefender, as they had a free trial offer for 12 months. So, after doing a bit of research, I came to the conclusion that it must be as good or even better thasn Kaspersky based on the reviews.
How wrong was I? Bitdefender has constantly been a pain, you always know it's there, and it's slowed down my computer (not just mine, I installed it on 3 laptops as well!) to the extent of being really annoying (and I have Dell Alienware with a 6 core processor).
Everytime you open explorer to see files, it's takes forever before the files are shown as it's scanning them. When you open the internet browser you get these busy icons on the goggle serach page while it scans the links.
I am now removing Bitdefender (even though it's free) and paying £100 for 10 devices over 2 years for Kaspersky. It will be worth every penny.