Boiling this down to a statement; Java gives you less functionality out of the box but provides you with more choice whereas .NET gives you more functionality out of the box but with less choice. It's the choice that I have a problem with. I used to think choice was great, but, after hours of research into Java frameworks and Java IDEs I've decided that too much choice is bad. I spent hours trying to figure out which IDE and framework was best before realising that the only way to find out is to use one for an extended period of time. Too much choice also dilutes the amount of support you get for each option. Take web frameworks for example; I've no idea how many people use .NET and how many people use Java, but say for example that 100 people use each technology. For .NET say that 50 people use Forms and 50 people use MVC. For Java, based on the number of frameworks I could think of off the top of my head (seven), say that about 14 people use each. I know these numbers are nonsense; my point is that because there is so much choice it's likely that far fewer people will be using any one Java web framework so the support for it will be significantly less. This is true in my experience. I often struggled to find help with problems using Struts and Struts 2. With ASP.NET I find there's rarely a problem that someone else hasn't already had and posted a solution for.
To summarise my experience, I'd say that you can get up and running much more quickly with a .NET web project then you can with a Java web project. There's far more functionality out of the box when using .NET, far less configuration and considerably more support. So if you're happy to cough up the money and you're willing to using Microsoft products .NET is the way to go.