Having compared notes with some architects that have worked on both platforms and having consulted with some people on some fairly complex application requirements where J2EE and .NET were both being considered, I would tend to agree that J2EE is "more complex" than .NET, as stated by Microsoft employee Frank Arrigo in this iTNews article.  From my perspective, this complexity is driven by the application server story for J2EE, a problem that doesn't manifest itself with .NET on Windows servers.  I'd be curious to hear from architects that are working with both platforms to get their perspective.