When comparing Windows Defender vs Avira, the Slant community recommends Windows Defender for most people. In the question“What is the best antivirus software for Windows?” Windows Defender is ranked 1st while Avira is ranked 7th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro No Ads
Pro 100% Detection Rate (according to AV-Test)
As of March 2021, Defender has been scoring perfect 6 in AV-Test ratings in all 3 categories for almost a year. The last time it scored a non-perfect score was in April 2020 which was a long time ago.
Pro Part of Windows
Pro Lightweight
Pro Fast, and free version seems powerful
I've used AVG Free in the past, and it seemed to slow my computer more than Avira does.
Pro Can install more components if you wish.
Optional installs include VPN, System Speedup, a password manager, browser extensions, and a hardened browser.
In the case that you've downloaded the Free Suite (not recomended), you can uninstall the above mentioned additional downloads with Avira's Connect app or any uninstaller utility software. This flexibility to cherry pick your extra software keeps the bloatware down somewhat.
Cons
Con It doesn't even get anything
Con Harder to set exceptions and restore for false positives
Defender and its options isn't as accessible as other av programs.
Con Occasional pop-up ad in the taskbar
The ad is nagging the user to purchase Avira
Con Extras like Browser Safety include offers/deals when you're shopping
This is exactly the sort of behavior users want to prevent when using antivirus and similar security tools.