Value: Investment vs. impulse buyGoogle Apps runs $5 per user per month, with no contract required. If you want to pay a year in advance, it's $50 a head. If you have 10 or fewer e-mail addresses to shepherd, you can get the basic Google Apps package free. The other Google products that I mention in the Features section are all free, all the time.
In the Microsoft tradition, Office 365 pricing is complex, even Byzantine. You can see some of the details in Microsoft's Office 365 Fact Sheet (Word file), but to see all of the options, you need to wade through the Subscription Plans site. At the risk of oversimplifying, prices range from $10 per user per month for bare-bones support with no Office license to $27 per user per month for the works.
I give Google a 9 for value. Office 365's value depends in no small part on whether you need or want to include Office Professional Plus 2010 licenses with the bundle. Assuming your company already has seat licenses for Office, I give Microsoft a 7, but if Microsoft offers you a rebate or discount for your current licenses, the equation changes considerably.
Reliability: The uptime factorOne final point didn't make it into the numerical comparison charts: reliability. Whereas Google has been offering Google Apps in various versions since 2006, Microsoft is trying to present Office 365 as a completely new system. Certainly one of the reasons for Microsoft's fresh new face is that 365's predecessor, BPOS, has achieved no small amount of notoriety for its reliability record -- or lack thereof.
Last year, BPOS crashed for protracted periods of time on August 23, September 3, and September 7. In response, Microsoft apologized, starting a new service called the Microsoft Online Service Health Dashboard that's supposed to keep customers advised on outages. Two problems: The Dashboard is visible only to paying BPOS customers, and it doesn't work when you need it the most.