They do both have all of those things. The difference is about the focus of the content.

First, TechEd is for everybody in IT - developers, operations, database, even management in some cases. The PDC is strictly about the care and feeding of developers.

Secondly, TechEd topics are focused on products and technologies that will are available now or in the very near term. The PDC tends to focus on things that are a ways off in the distance. So this year's TechEd focused on things that are shipping or will ship by the end of the year (Visual Studio 2005, .NET 2.0, Exchange 2003, etc.), PDC will likely discuss technologies that don't even have product names yet (Longhorn, Avalon, Indigo, WinFX).

HTH