I use both Malwarebytes as well an Avast, i use Avast to scan webpages,files etc in realtime and i use Malwarebytes simply to scan my system every once in a while.
Malwarebytes is a pretty reputable and reliable anti-malware program and i have yet to run into any issues using it so i would say your friend is right in that regard. Granted there are other anti-virus programs (like Avast) that i don't think are "crap" as your friend claims.
But any protection is better then no protection, even if you have an anti-virus program is not fully reliable in detecting all malware. It's better then nothing.