Well, we can't tell you which is "best" as that is up to only you! But, we would love it if you tried out Avast for Mac. (In fact, we have a free antivirus for Mac, which you can upgrade for more features if you like.) Mac Security can protect you against a variety of threats, including malware/viruses as well as malicious URL's.
Avast Free Mac Security has real-time protection plus the ability to also detect Windows threats. This can help prevent you from inadvertently sharing infected files with friends who are on Windows.
Hope that helps and please let us know if you have any questions!