From a security perspective, they are both only as good as the controls you put in place. Which ever one you go with I recommend you apply Password standards and have MFA switched on. Also, make sure you keep customer information separated to avoid accidental breaches – this one can be as simple as having separate folders for each customer.

As you have the subscription for Office 365, I’d suggest sticking with that if you plan to do most of your work in Word/Excel as the integration between those and OneDrive is more intuitive than trying to open files from Drive. It also gives you access to a range of other tools for one cost that can be useful to your business (i.e. Bookings).

If you decide to go with Google then consider scrapping the Office 365 subscription as you don’t want to pay for two once the free deal roles off. Only do this if you’re comfortable working in Google docs/sheets though. Also be aware that you may end having to pay for other tools that come “free” in office 365 (I.E. Calendly)