Have you considered learning both? They have a lot in common, and 'which one is better' is a decision you need to make for yourself in the context of your project.

Oddly enough, geography might matter. For example, Seattle seems to have a bunch of consulting shops and even a few product startups using MS tools. (There are also startups using the usual suspects...Java, PHP, Python, Ruby,...).

Both languages' VMs are accessible to a number of other languages if you decide to branch out later. As many have said already, Java gets a slight leg up from open source.