What are the benefits of switching from an online mail/calendar to desktop clients?

I have gone back and forth, having used Outlook as well as Thunderbird and Forte Agent, but I always go back to the web apps, which is what I prefer now. Everything else seems reduplicative when you have Google Mail. Even if you sync mail and calendars there doesn’t seem to be much point in using a desktop app.

The reason I use a desktop mail client, desktop calendar, and desktop RSS reader is because I am often times without internet, and will still need to use said calendar, emails, etc.
I also like having a hard copy on my hard drive if the online service fails (I’m pretty confident with gmail, but I did use ma.gnolia at one time)

I just like having a backup, and not being so internet reliant all the time. There have been many times where I have needed to dig through a calendar or email message looking for something while offline.

Gmail and Google Calendar both have off-line modes.

Yeah, I know. I tried them for a little while, and just ended up going back to where I was. I just sync Google Calendar with iCal anyway, so it works a similar way.
I just do what works for me.

I don’t see a benefit. I use many computers (home, laptop, work, library, friends’, relatives’) and I can always check my email and calendar. I also have my WWW bookmarks synced with Xmarks.

If my computer were stolen today, I could replace it in an instant without missing anything but my MP3s.

I back up my GMail using Windows Live Mail (the Windows 7 replacement for Outlook Express), but I never actually read mail with it. Other than backup, I haven’t used a desktop mail or calendar app for years.

I suppose performance could be a reason. That isn’t enough of a benefit for me personally though, especially with today’s fast webbrowsers.