This thread’s title is Malwarebytes vs. CleanMyMac X. While the OP may be mostly interested in malware protection, comparing both apps in their entirety is still relevant, especially since it seems (to me) that (1) both apps’ malware protection is probably good and reliable, and (2) neither causes problems. (An older thread here https://talk.tidbits.com/t/current-recommendations-for-anti-malware-software-on-the-mac/18679, though a bit dated, speaks to this issue, and includes what seem to be some wise words about the need for malware protection on Macs.)
Malwarebytes is free (with also a paid premium version) a one-trick-pony. CMMX additionally has many clean-up routines, and the one-user cost is €40.00 ($43.00) yearly. I believe these are quite useful, and I use them regularly. (Since I lost all my data many years ago, not due to malware, and have experienced a few other problems now and then (like slow-downs, faulty Spotlight searches, messed-up perms) I also use OnyX and TechTool Pro (as well as good back-ups) to try to protect myself as much as reasonable and possible against glitches, and it seems that I’ve been pretty successful.) All this my be overkill in the eyes of some, but not for me.
So, bottom line: I like what CMMX does, I feel it’s not expensive, and the price is worth it. And, as I said, I like the company. YMMV.