While Google Apps costs $5 per user per month (or $50 per year), Office 365 starts at $2 per user per month for just basic email, moves up to $6 for a small business package and up to $27 per user per month for an enterprise option that includes all the online offerings plus the non-cloud Office Professional Plus.
Some of the Google features that aren't included in any version of Office 365, Sinha writes, are "data export capabilities to prevent lock-in" and multi-user editing of documents and spreadsheets for mobile users.
While Google offers email archiving for an extra $1 per user each month, Microsoft customers have to pay at least $24 per user per month for a plan that includes that feature, he writes. Sinha acknowledges that some features in Office 365 aren't available from Google, including unlimited email storage and hosted voicemail, and an on-premises PBX voice system.
"Apps isn't for everyone," Sinha writes. "But in the last week alone 38,000 businesses decided to give it a try. Maybe you should too."
Google claims more than 3 million businesses use Google Apps, and the company just launched a line of Chromebooks, Web-only laptops that don't require Google Apps but may be effective for Google Apps customers.
Microsoft's publicly stated numbers are a bit higher: 750 million active users of Office, and installations on 1 billion PCs, although Microsoft doesn't detail how it arrived at those calculations.
Microsoft CEO Steve Ballmer is scheduled to talk to press in New York City Tuesday to announce the launch of Office 365. Microsoft is likely to argue that it's better suited than Google to providing a full-featured and secure office experience, whether in a customer's data center or in the cloud.
But there's room in the market for both, and Google has won some converts. Sinha hopes Google's cross-platform capabilities will win some more.