Disadvantage of Removing Antivirus from Laptop

First off if you have Defender, you have an antivirus program (and it works well). And you should never run a system without any antivirus program. As for McAfee, I am not a big fan but other seem to like it and it has gotten good reviews. My personal favourite is Bitdefender which seems to have little or no effect on system performance. And there are some very good free antivirus programs that you can look at (AVG and Avast for example) . The link below should give you more information on Defender.

https://www.pcmag.com/review/171496/microsoft-windows-defender-security-center

https://www.maketecheasier.com/is-windows-defender-good-enough/

I remember reading an article about some of the most common behaviors of information security experts that seem unintuitive to regular users.  The first is that they use password manager applications, and the second is that they do not use third-party anti-virus.  I use Windows Defender exclusively, because a) Defender actually holds up quite well against the competition in independent tests, even though it's free unlike many other offerings, and b) I've found that third-party anti-virus seems to cause more problems than it solves, especially in these days of new Windows 10 releases every 6 months.  Anti-virus has always had the potential to block or slow down legitimate activity that the user wants.  As just one example, I'm a big fan of Macrium Reflect for disk imaging and cloning, and the Macrium forums have many threads where third-party anti-virus turned out to be the reason that various operations took a long time or were completely blocked, sometimes without any notification from the AV solution that it had interfered with anything, making it more difficult to diagnose.  Then there's the reality that third-party AV hooks into the OS in ways that Microsoft does not recommend and explicitly does not support.  As a result, there have been many cases where users running third-party anti-virus have installed Windows updates and then found that their system is unbootable.  Of course the users blamed Microsoft, but the true underlying cause turned out to be that the update changed something that third-party applications weren't supposed to be touching anyway, but some AV solution was doing it anyway, and that took down the entire system.  That risk is greater these days with Microsoft releasing major Windows 10 updates every 6 months.  Then there are documented cases where AV solutions have become a security vulnerability.  It turns out that when your application hooks into an OS deeply and pervasively and starts monitoring everything that's going on, as AV solutions do, then an error in your code can be exploited by just about anything on the system and be used to gain low-level privileges to the system.  I remember an article recently about Norton anti-virus having a vulnerability that could be exploited remotely because Norton was scanning all inbound network traffic, so if you sent specially crafted traffic to the PC, you could trigger a bug and gain low-level access to the system.

And some AV solutions expect you to PAY for the "privilege" of all this!

Just an update. I actually had to uninstall Bitdefender as it was causing my Internet speed to slow way down and rebooting the system was the only way to recover. But after a bit of time the slowdown reoccurred. I now use Defender exclusively and also installed Malwarebytes. Now my Internet speed is unaffected. And no I do not have Smartbyte installed. I clean installed Windows 10 the first day I received my laptop and my main system, a desktop, is not Dell but a home built.