I too have liked to use Microsoft Security Essentials (aka Windows Defender in Win 8) as the real-time scanner, with additional on-demand scanners such as Malwarebytes installed, just in case.
Otherwise I'd used Avast as the real-time scanner (but chose not to install all the extra components that they've added over the years, especially on slower computers). Or if you do use MSE, can still keep Avast around as an on-demand scanner.
IIRC MSE started with a great reputation for providing competent protection while being so lightweight. But in later years, I think the AV testing sites found that the competition has started to eclipse it in the scope of its protection, such that MSE is now often considered a baseline product. Some say that Microsoft has no problem with this, perhaps as not to tread on the 3rd-party industry?
Kinda gives me mixed feelings when using MSE on family member computers, cuz some seem to blindly click on links they get in emails