My personal thought is that, for a machine with more than a simple MyWebsearch type "infection", you need BOTH Mbam and Sas.
On infected machines, I always run Mbam first because it will usually install when viruses are blocking Sas from installing. After Mbam installs and reboots, I run Sas and it finds tons of bad stuff Mbam didn't. Reboot, back to Mbam...you get the idea. Oh and obviously, I check for updates every time I reboot.
I've run Mbam (or Sas) two times in a row with 0 infections found, then run the other program and find several more infections that were undetected by the other. Pretty amazing, but I like them both.