Thunderbird vs gmail/yahoo, etc
Here are some reasons you might choose to use a native application email client instead of something like gmail & yahoo mail.
1. Stability - A lot of these web based email clients change day to day.
2. Reliability - Thunderbird's reliability is very solid. Web based clients can be very quirky.
3. Speed. Native clients tend to be faster than web based apps.
5. One click open for native apps versus login procedure for web apps.
7. No ads.