It's not a guarantee but I'll trust Google for application security over Microsoft every time.
That said, it's not the question. The question is if a company wanted to switch away from Microsoft here, what is their option? It's not an inherent statement that one is actually better, but that there is an option if one feels burned by Microsoft here.
I’d trust them marginally better, but certainly not orders of magnitude more. We don’t know if Google would do significantly better if they operated at the same scale as MS in Enterprise. Google operates some consumer properties at an even larger scale, but I get the feeling that Enterprise is particularly attractive to hackers for the potential rewards.
Last week Firebase sent me a notification that several of my properties (some of them enterprise apps) had lost domain name verification. The panel in the console was clearly glitched when I inspected it. Two days later they sent a correction saying that this had been a mistake. No big deal, but it goes on to show that Google is not perfect.
I'm not sure what scale would affect this that Google hasn't already hit? I've already had GSuite for my high school, my college, and my work. What additional scale would open up massive security holes? This seems like it's very much just horizontally scaling the same product.
Not to mention that GSuite already has 6M different customers/tenants. They're already at a comparable scale, and that doesn't mention that the free versions have the same application security model, with zero incidents (knock on wood). "but scale" feels like it's ignoring the already existing track record and scale and just making excuses for Microsoft.
That's 6 million, vs. the 260 million that Office 365 has.
And that's individual licenses. I can't easily fetch the number of medium to large companies on Microsoft Office vs GSuite but I wouldn't be surprised if it was significantly larger than 50x.
My original contention is that hackers may be particularly interested in that dimension, rather than in the number of individual licenses (which MS also dominates by an order of magnitude).
I do not believe without data that switch from one closed source proprietary software provider to another one will guarantee you from hacks.
Switch to open source most certainly does not. Nor is switching from one proprietary provider for your software from Microsoft -> google