Frankly, I don't think we can correctly compare MBam v.1.75 to the newer versions (v.2.1.4.1018) Premium due to different/improved technology/Engine etc which to achieve better security, takes more resources
** Just as I don't believe we can correctly compare Older versions of Avast (say version Seven or Eight) to version 10 (2015) for the same reasons; different/improved technology/NG etc which to achieve better security "also" takes more resources.
I have used the Paid versions of both MBam and Avast for years and they have changed. As they have developed, it can be stated They 'both' have gotten better at providing more security and on my OS's they both consume more resources and seem heavier then earlier versions I've mentioned.