This lifehacker's definitive comparison did a pretty good job comparing the most two popular email tools, in a business aspect. The conclusion that Gmail wins though shouldn't be the key point when choosing the email platform.
My point, simply is, for a company with less than 20 users go for a Gmail solution. For any company with more than that, going with Outlook with Exchange is a no brain.
Home user? Always go for Gmail. Or if you really like Outlook, use it with Gmail IMAP configured.