It makes no difference if it were avast free and MBAM Pro, whilst they are resident applications they are different. Essentially not having two resident anti-virus programs installed or not having two resident anti-spy/malware applications installed.
One of each generally isn’t an issue. After that on-demand applications can be used as an alternative second opinion. But there are precautions that can or should be taken to take them out of direct contact/conflict as I have mentioned.