I haven't used G-Suite in years so I can't really compare it, but I use Excel online (via Office 365) to collaborate in real-time on documents with other employees all the time and it works great.
Where G-Suite suffers is in the random features that a small segment of power users swear by. The keyboard shortcuts aren't the same as what people learned in Word/Excel. There are many incompatibilities and rendering issues with the Excel and Word formats. But these concerns apply mostly to advanced users; for basic documents, letters, lists, and tables, G-Suite in 2018 works well
You can do some of these things in open formats like .odt and G-Docs will be better about this. However, there are still problems with things like pagination.
So overall, I think Docs is where you want to be unless you have some super niche use case. I don't have enough experience trying to do crazy things with Sheets to have an opinion on it vs Excel though.