Free vs. subscription...
SharePoint Services is free. Google charge a subscription per user, per year.
If you can get by without the functionality of SharePoint Server product (the one they charge for) then SharePoint services may be just the job. I'm coming round to the FOSS thing. Some of these open source products are getting pretty fit for market now.
I've looked at the Google stuff and it all seems clanky and I'm not sure how far I trust Google. Any company which thinks that Wi-Fi data harvesting excercise was acceptable has an approach to data which I am not happy with for my business.