Java and .NET seem to have a great number of parallels especially in the web application area. Both languages have many of the same technologies especially in terms of open source libraries (JUnit and NUnit, Hibernate and NHibernate) but there are also plenty of differences and different approaches to solving certain software development problems.

As a Java developer I get the feeling I'm missing out on learning about web application development from the .NET point of view and I could learn a lot about the general principles by learning two languages rather than getting stuck in the details of Java and not seeing the bigger picture.

So the first question is, do you agree? Does learning two separate but similar languages such as Java and .NET make you a better programmer?

Secondly, I'm worried that if I choose to take, for example, a MCPD ASP.NET 3.5 certification it won't actually help me get work doing .NET development because it goes against all my existing experience. Is trying to broaden your skills a good career choice or is it a better decision to choose one technology and stick with that?