Well that depends on the device you compare it too and just what you are protecting it from.
The reality is MACs are technically safer if you are comparing them to Windows devices and it comes down to two basic reasons. However, it is for these two exact same reasons that Chrome Books are even safer than Macs. So I guess it's time to update those Mac vs PC commercials, Google.
As Linus from Techquicke explains in this video a big part of what makes Macs safer is that inherently those who write malicious code prefer to cast a wide net and target the larger pool of potential victims. Currently and for a very long time that has been Microsoft PCs. Microsoft also makes up the largest segment of devices in the business world, a high priority target. For this very reason, it stands that Chrome Books being newer to the market and much less used is the even safer option.
The second reason and one not talked about much in this video is that Macs are a much more closed down echo system making it harder for malicious code to damage the security system without authorization. Something that is quite easy to get around in a Windows-based system although Windows 10 has done a lot to improve upon this. Of course, ChromeOS is even tighter with almost no way to download or run malicious software. Hence making it one of the safest devices to use in both scenarios.
Of course, none of this really matters and thinking you're safer on one system over another only serves to benefit the people trying to hurt or steal from you. Times change and tactics evolve. PCs and high-end Macs are getting more and more expensive, it is only a matter of time before those users become more valuable targets.
The number of Apple and Windows users I meet that don't routinely update their devices or practice good user habits because they unknowingly have bought into the idea that Macs are safer or that anti-virus software will protect them, astounds me. The biggest weakness of any system is the user sitting or sometimes standing behind it.
At the end of the day, things like phishing, man-in-the-middle, and ransomware attacks don't care what your shiny new computer looks like and can target anyone on just about any system. So don't fall for the marketing hype, keep your software updated and maybe educate yourself on how not to fall victim to some of these scams.