Gmail used to be snappier than Outlook is now when it launched, even as a webapp. I'm not sure quite how they've managed to mess it up so badly, but it's poor engineering not a limitation of the tech stack.

Agree with you on the other office products though. Word, Excel, etc aren't perfect, but they're much better than the alternatives for most things.

I've been forced into using Outlook on Windows and Mac and snappy has never been my impression, although I seem to recall it being somewhat more usable on Windows. Not that GMail is snappy either, but a browser based client isn't necessarily slower than Outlook. Although an actually fast native client would be hard to beat.