1. We were still paying a subscription for Office while on G Suite, the cost to change to fully O365 was at worst net-neutral, but definitely saved about $5/mo per head on paper.
2. Calendaring for Google sucks. We're a distributed team, we have recurring meetings, and lots of updates across various devices. Meeting updates were frequently not persisting to users, cancelled recurring meetings were not going away, etc. Heaven forbid you have someone that wants to cling to Outlook as their mail client, because then you'll have a whole host of other issues.
Outlook/Exchange may be 'non-standard' as far as not playing by the specs, but it really is the standard for anyone who's spent time in a big company, and it was getting really embarrassing when our Google Calendar invites were not playing well with our potential and current clients' Exchange systems and Outlook clients.
I do miss the Google Apps sign in to all the various services we use. Some have integration w/ O365 or generic identity authentications, but most either don't or charge a lot extra. Other than that, I don't miss a single thing from G suite that O365 doesn't do just the same or a little better.