I own an IT firm and we support and resell both products. Most of my clients go with Office 365 vs Google's G Suite for a few reasons:

1) They are used to the MS Office feel. Word, Outlook and Excel.

2) The new pricing model of Office 365 helps small businesses have the cloud and installed versions of MS Office.

3) Most businesses they work with use MS Office. If they go with a different solution, formatting of documents becomes an issue.

G Suite has many features that are appealing to some clients, such as the live editing (multi-user editing) and ease of file sharing. Plus a more "user friendly" management portal (however, this is changing :/ )

As some noted, it all depends on your needs. If you just want email, I would say go with G Suite. If you need Word, Excel, PowerPoint, etc, and email go with Office 365.

Note: Do not purchase MS Office standalone versions, you can buy 2-3 years of Office 365 with email and the same apps.

I hope the above helps. Feel free to message me if you have any question.