Earlier quoted context omitted.
Microsoft Defender typically doesn't hurt performance or security much. The alternative is to run Mac or Linux stacks instead of a Windows stack, of course.
While running a Linux stack may still work, your Mac info is outdated by three years, at least. Macs have entered the zoo in 2015.
What "zoo"?
To this day, Macs are practically virus-less, which they always where (99.999% of the scares in the media were for trojans, and even those at worse affected something like 1-5% of the total user base) -- nothing like the good ole Windows (XP and pre) days where after 1 day surfing the web you'd have a few viruses.
And of course if you go with the default options (gatekeeper, signed packages, etc) you have even less to worry about.
It's also not about "market share" -- Macs had 1/4 the market share they have now in 1990-1997, but there were tons of viruses for them under the old OS.
It's not like the original (pre-many security features were introduced) OS X was specially hardened or anything, but it was much more secure than Mac OS and the old Windows versions just by having a basic UNIX-style design.