I don’t have a dog in the fight, I don’t choose Gmail or Outlook. But if I were to play devil’s advocate, I think I would argue Outlook is better on the grounds that Microsoft is not an advertising company. As a company, they don’t depend on distributing free software to folks who are willing to, or maybe ignorant they are trading their personal privacy in exchange.
No doubt Microsoft is trying to monetize user data at this point as well, but their empire isn’t built on top of it. The parent comment said they use ProtonMail for personal, So I suspect they only reason they don’t choose that for business also is the weight the Microsoft name still holds.
Many of us got sucked into the Google vortex a while back on the basis they gave us many of the best software options, in many categories. But at this point, there is nothing Google does that you can’t find an alternative of equal or better quality. So if one day a person realizes Google values don’t align with their own, slowly phasing out all Google services can only have a net positive.