Avast free:
- Pros:
+ always up-to-date with streaming updates which deliver tiny signature packages frequently
+ extremely low memory usage: both physical and virtual
+ easy on disk usage especially after tweaking
+ very customizable, can modify almost every option except for a few
+ modular installation which allows removing/adding components you want
+ very powerful hardened mode against exe malwares which works regardless of the file tag, unlike smartscreen which works only if the file has the tag of being downloaded from the internet. It works flawless in conjunction with syshardener or any script blocker. This combo yielded 100% protection in MT hub for a month
+ can be tweaked for much faster performance
- Cons:
+ ads, popups, bloatwares and privacy issues
+ buggy especially from its behavior shield and hardware virtualization feature => both can be disabled
+ unoptimized web shield which can cause higher CPU usage while browsing
+ so-so webfilter, more effective than most but not as good as the other 2
+ very poor phishing protection because web shield doesn't include the latest phishing database. It only includes frequently visited phishing pages. The latest phishing database only includes in Avast Online Security extension
+ not good against script based malwares, so-so against ransomwares (default settings)
+ so-so against PUPs, still better than the other 2
+ must register for a new free license yearly, or it will completely stop working, literally (AVG doesn't require any license but lacks hardened mode)
Kaspersky free:
- Pros:
+ relatively lightweight after tweaking, still feels heavier than avast due to its slow scanning speed and cache wiping after system restart (noticeable when opening a folder with full of exe files despite scan on execution is enabled)
+ The best signatures, cloud and behavior blocker, period
+ very effective (post-)exploit protection
+ one of the best web filters, better than the other 2 in comparison
+ strong BB against ransomwares
+ can be very customizable
- Cons:
+ not always up-to-date, sometimes signatures are outdated without automatic update
+ heavy web filter and very buggy. Frequent problems with its fake certificate. Code injection increases CPU usage significantly, can be disabled
+ high virtual memory usage, easy on physical memory usage
+ not so good against PUPs and adwares, improved by enabling an option
Bitdefender free:
- Pros:
+ good signatures, good webfilter, not as good as kaspersky
+ stronger BB than avast, not as good as Kaspersky
+ quite light after a week of using, not as light as avast
+ easy-to-use UI
- Cons:
+ very limited customization
+ not always up-to-date, can't trigger manual update.
+ nags, which can be disabled
+ cloud feature is very poor compared to the others. It works when the signatures are outdated only and only on execution. I've never seen it detecting anything when sigs are fully updated
+ really heavy on virtual memory usage, easy on physical memory
+ not good against PUPs, adwares -> CAN'T be improved due to a lack of settings
+ freezes the PC when updating. Large signature packages
+BB is useless against zero-day MBR-encrypting ransomwares (petya, nonpetya, goldeneye,...)
+ not the lightest webfilter
