Short and sweet. If you use both Twitter and Facebook you should be using Seesmic Desktop.

Why?

• It looks good and doesn’t use a lot of memory
• User lists – you can make lists of users to be sure you don’t miss their tweets
• Facebook status – update your Facebook status from within Seesmic
• Facebook comments – someone comments on your status? You can comment right back from within Seesmic (no having to log in to Facebook)

But, what do I know? Try Seesmic Desktop for yourself, follow me on Twitter then let me know what you think.