I use both. I have 3 email accounts, two of which have a webmail interface and one that does not. I primarily use Thunderbird but don't delete messages for n

I use both. I have 3 email accounts, two of which have a webmail interface and one that does not. I primarily use Thunderbird but don't delete messages for n days (well never for gmail) so I can also check with various webmail accounts. Among other nice things the ability to filter out HTML is a "killer feature" I simply can not live without and have yet to see duplicated in any webmail interface.