Ive used the free version of this software alongside Norton Security, and the two programs have played nicely together for me across several different devices for quite some time. Malwarebytes has always been very light on my system, and there did not seem to be a significant change in background load when running it with Norton, so I was very confident that running the full Malwarebytes program alongside Norton would go as smoothly as it has.
Both programs seem to readily detect certain things faster than the other, so between both programs, my computers (especially my gaming laptop, which I use most often these days) seem to actually run better with both programs running.
Malwarebytes is a bloodhound when it comes to web surfing/web protection and live threats, and does so without all of the crazy toolbars and add-ons that Norton typically tries to install on browsers. On the other hand, Norton has been excellent over the years at quickly blocking or catching registry attacks and preventing overall system instability, no doubt due to how extensive the Norton network is and the PC threat data analytics attached to that. Malwarebytes uses a live behaviour-based threat ID system that seems to be benefiting my devices in a way that Norton and other programs have not done to the same degree thus far. Norton identifies new threats fairly quickly, but sometimes has to clean them up after the fact since it does not identify threats in the same manner as Malwarebytes does, whereas Malwarebytes may lack the data of Norton but more than makes up for it with the behavioural analytics it employs.
I'm giving it a 4 since I have yet to solely depend on Malwarebytes alone, but it is a very strong 4 since it has an intuitive user-friendly interface, is not a resource hog on my devices, and since Ive completely and regularly seen its unique comparative benefits in action. I definitely recommend Malwarebytes, although from my perspective, it seems to work best in tandem with a compatible antivirus program.