I think as already mentioned that Defender and malwarebytes is a great way to protect your system
also consider comodo security suite (Free) and malwarebytes.
On occasion I also run the Kaspersky rescue disk (thanks Kaspersky) about once a month
Kaspersky Rescue Disk 10
Add a giant dose of common sense and maybe something like Ghostery to you browser you should be okay
It's AV's job to meddle into everything or most anything going on in the system. That has to have some impact, more protection, more impact, it's unavoidable. Fortunately or by design it's not measured by percentage of CPU, RAM or disk usage but have set values in any system. Take one AV, turn off all but one core of the CPU and slowdown will be quite noticeable comparing to when let's say all four cores are running. So you can't compare impact of one AV on computers that vary a lot by their performance.
Benchmarks I found are mostly HW centered so they are not much influenced by AV's presence. Monitoring let's say disk performance in real time with or without AV will tell you more.
1) Are you someone who will open & close a lot of programs/windows while using PC
2) Have you had a chance to use a really fast PC with no AV and a ton of other programs installed?
If answer to both is yes, then you will definitely notice the difference. Of course, if you've had a 3rd party AV for years and got used to same slowness on start-up and while it's searching your PC, then you probably just think it's normal for things to work that way.
There really is no reason to use anything other than MSE if you know a few things how stuff works on the internet. I've worked in an IT company and repaired computers on daily basis and the reason people had a ton of malware and stuff like that was because they would click anything and everything, download various stuff from unknown websites and emails as well.
But at the end of the day, each user uses their machine as they want. If someone has one, two or even more 3rd party AV/anti-malware and similar programs installed and they're fine with stuff being slower than it could be, then that's up to them.
OTOH if you have Windows XP, not running with Defender, nor MSE, nor Windows Update, nor Windows Error Reporting, nor any Malicious Software removal tool, and just a low impact 3rd party antivirus, such as Baidu, the speed it runs at is amazing, if not comparable or superior to Windows 10 on the same hardware.
Ah yes Microsoft Security Essentials, wasn't this pre-Windows 8 and Windows 10 software days??
It is really the only anti-virus I use in conjunction with MalwareBytes.
2) - We've all had IT jobs and have opinions and thoughts on how things work and should be. Nothing new here.
3) - Arguing about fractions of a second an AV program "may" add is a waste of time, especially when it'll hardly be noticed by those doing daily tasks on their PC's. I know I'm not sitting here sayin "man, my PC could be so much faster if I didn't have that AV installed". Why... because the only time you may really notice it is during start-up and shut-down, and that's not a major daily task of using a computer. In short, it's insignificant.
4) - Yes, we run our systems as we see fit... even if others disagree.
Bottom line is I think this argument is much to do about nothing.
Yes, I can run computer without any protection too but time i have to spend by being extra careful is far longer than eventual slowdown caused by adequate protection. Only some common sense plus some protection without great impact on performance and undue risks. For me and like me with a lot of experience that should be enough but to tell somebody just starting or without any knowledge or not caring to go on internet, swap files etc. I would never recommend any less than what I use but also much stronger protection and even that in many cases is not enough. Even for the price of slowdown it's better in such cases to be as protected as possible than to loose everything. People that don't know much about safety, usually lack the knowledge to do proper backups and to get out of eventual tight spots.
Been using MSE since it was introduced back in 2009 without any other antivirus, and to date have had no problems or viruses, thus really see no reason for anything else. . . Also this thread is really fun to read. . .it also shows how Swagger is showing again just how full of himself he truly is. . .