If you’re looking for the best free antivirus software on the market today, then a few popular brand names will keep appearing on your Google searches. You’ll notice that Windows Defender and Avast are two of the most popular PC antivirus programs available to users today.
Why are these programs so popular? And which one is better than the other? Today, we’re going to provide a brief comparison in order to show you which one to download on your PC.

User interface

Aside from the recent Windows 8 debacle, Microsoft has always been really good at creating user interfaces. Windows Defender is no exception to that rule, and I’d feel comfortable installing Windows Defender on my grandma’s computer knowing that she’d be able to figure it out. The brightly-colored buttons and simple four-tab menu system makes scanning and updating your computer a breeze.
Avast isn’t a bad program, but it’s not designed to be as simple as Windows Defender. To make matters more complicated, users constantly encounter paywall restrictions when using the software, and Avast is always trying to upsell you on the full subscription-based Avast software. That’s bad if you’re just looking for a simple, free antivirus interface. Windows Defender takes this category hands-down.
Winner: Windows Defender

Features

In the previous category, we talked about how simple Windows Defender was to use. That simplicity is its downfall in the ‘Features’ category, which Avast wins easily. Avast is packed with features. Even the free version – while still carrying plenty of restrictions – gives users access to all the features they would need and more, including a number of real-time online protection shields (for IM, internet browsers, P2P software, and local networks).
Windows Defender doesn’t have these features – but it’s not built to have these features either. Windows Defender is designed to be a simple antivirus program that scans your computer when needed, which is why Avast wins this category. Sorry, Windows Defender, but most PC users demand a little more out of their PCs in this day and age.
Winner: Avast

Protection

Obviously, the most important quality you should care about when comparing antivirus software is the protection rating. Windows Defender has frequently failed security tests performed by third-party companies. Avast is no shining star, either, especially compared to paid antivirus programs, but it’s slightly better than Windows Defender at keeping viruses off of your system.
Winner: Avast

Performance impact and speed

Back in the day (like in 2005), antivirus software was such a pain to use that few computer users even bothered with it. Antivirus software slowed computer performance to a crawl and made browsing the internet basically impossible.
Avast uses more resources than Windows Defender, but it completes scans more quickly. Expect to wait for around 20 minutes for Windows Defender to scan an average-sized hard drive, while Avast can complete the scan in about 5 to 10 minutes for the same amount of data.
Winner: Tie
Both of these programs are powerful, but if you’re a power PC user looking for the best features and performance, then we recommend Avast. If you’re looking for a simple but effective antivirus program to install on your computer (or your grandma’s computer), then Windows Defender will work just fine. However, with Windows Defender repeatedly failing verification tests from third party organizations like AV-Test, we’ve got to give the overall edge to Avast in this comparison.