Some say they compliment each other well... Others say you should not use them together. Lots of people have them running side by side with no issues at all.
There is a mountain of research you can do on it, but I think it comes down to your individual set up. If it works for you, I'd say use them both. I've had Malwarebytes PRO since around 2007 and aside from one issue, it's always been a great tool.