I run malwarebytes every now and then on customers machines.
But honestly all I use if avast. But this is because I always make sure my java and flash are up to date. 90% of viruses come in through them and if you keep them up to date you plug those holes
I haven't been infected in years. And the one time I did was because my java and flash where out of date.
They use to infect you by going through holes in IE. When people started using other browsers they need something all of them use. And that is java and flash.
Shane