When comparing avast! vs ClamXav, the Slant community recommends avast! for most people. In the question“What is the best antivirus software for the Mac OS?” avast! is ranked 4th while ClamXav is ranked 10th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Decent anti-virus protection
Pro Monitor directories easily
The Sentry Feature monitors specific directories 24/7 as well as removable media which includes USB & external drives, all those .dmg files you open when installing apps etc. I add all directories that files are downloaded as a "screening" process.
Pro Lean
Not overly invasive or processor hungry as other antivirus programs
Cons
Con Tries too hard to sell you the paid version
Con Too noisy
Avast! has sounds turned on by default. It also has a lot of blinky features of questionable use.
Con Makes your system slower than usual
Even though scans are not being run in background, it will slow your system.
Con Opt-out installation of Google Chrome
These advertising tactics are simply unacceptable.
Con Selling potentially identifying user data
Con Detection rate isn't too solid
Avast! is not the sort of antivirus product to give you peace of mind. In practice, it does miss some malware every now and then. You'll need backup virus protection, which raises the question why you should get Avast in the first place.
Con Expires after a year leaving computer exposed to new viruses
Expires and stops updating after a year after which the user's computer may become infected by new viruses not covered by existing patterns.
Con May interfere with hyper-V
Since avast has its own virtualization engine, it will cause issues with hyper-V.
Con Unable to detect some adware such as FADE adware
Con Blocks or causes issues on apps or games
Con "Smart Screen" feature
When running an unknown application, avast will run it wrapped in a sandbox environment first for scanning, then kill the process and re-run it again. A lot of applications do not like this.