Er... One teeny tiny little thing. They're comparing Gmail (webmail) with Office (a client). It would be more accurate to compare Gmail with Hotmail which would entirely speak for itself (BWAHAHAHAHA!).
Also, Gmail supports IMAP and POP, so you're entirely able to use whatever client (Thunderbird, Office, whatever) you feel like.
Gmail is also linked with Google Calendar, Docs, iGoogle, Google+ and all the other I Can't Live Without It stuff Google is pretty much renowned for.
Oh well, nothing new seeing Microsoft misrepresent the facts.