It depends what functionality you want -- obviously if connecting to Exchange IM and
SIP-based communications servers is important, you may want to consider upgrading to 5.0.
Other new features of Windows Messenger 5.0 include UPnP file transfer and TabletPC "digital
ink" support. However some features were removed, like Add-In support (which means, no
Hotmail, MSN Profile or MSN Mobile support).
Microsoft MVP - Windows Messenger/MSN Messenger
Messenger Resources - http://www.yqcomputer.com/
there is an upgrade to version 5.0, but I see there is an option to upgrade with ability for
SIP and exchange and the other doesn't. Which one is better?