A recent project of ours changed that. We’ve designed and set up an automated lab of 10 PCs (not virtual machines, but very real ones) with 10 most popular antiviruses: Kaspersky, Comodo, AVG, ESET, McAfee, Malwarebytes, Avast, Microsoft Security Essentials, Avira and Norton.
The lab automatically ran several dozens of different software installers, some of which included potentially unwanted software (like ad injectors), and tested the antivirus responses to each one of them.
So we chose ESET. Why? Because some reports suggested it was the most light-weight solution in terms of system resources.
Oh, and there’s a Mac version too.