Greetings Tom,
Actually they're not the same GUI and don't support the same things.
MSN Messenger 6 has support for display pictures, custom emoticons, has a different
interface, etc. whereas Windows Messenger supports SIP-based communications services,
Exchange IM Server, etc. Which one you use is up to you, and a matter of personal choice
(and based upon your needs and likes), however one thing to keep in mind, Windows Messenger
must still be installed on Windows XP in order for MSN Messenger to retain full functionality
(Remote Assistance, Whiteboard, Application Sharing, etc.).
MSN Messenger is centered around MSN technologies (Hotmail, MSN Member Profiles, MSN Mobile,
etc.) whereas Windows Messenger is centered around Windows technologies (Exchange Server,
Office Live Communications Server, Windows Netmeeting, etc.).
Both clients however can make use of Microsoft technologies, like the .NET Messenger service,
..NET Passport and .NET Alerts.
____________________________________________
Jonathan Kay
Microsoft MVP - Windows Messenger/MSN Messenger
Associate Expert
http://www.microsoft.com/windowsxp/expertzone/
Messenger Resources -
http://messenger.jonathankay.com