I've noticed that no-one has talked about the cost of using either.
Yes the Java IDE's are somewhat inferior to MS's, but you can get everything you need to write, develop, manage, and host Java applications for free compared to MS; the OS, IDE, Web Server ... all cost money which can be a substantial amount for commercial purposes.
Or, if you can find a Network Partner, join the BizSpark program and use their stack for free for $100 after 3 years: http://www.microsoft.com/BizSpark/
The argument of Java is better because it's cheaper tends to fall apart when you look at that.
I agree it might be more productive (I've never used it). But I do feel the costs and associated costs are quite high.
Imagine you get accepted by PG into Ycombinator and you have your $15000 in hand to start. Using MS technologies you have to pay ~$700 per developer for a Visual Studio license: http://www.amazon.com/dp/B000WM04HU . As you are now a commercial enterprise you can't use the cheapo student version for $50 anymore. Plus you need to pony up a IIS license for each developer to test on, and Windows Server 2008 license for each developer, and an even more expensive OS license for your multi-processor multi-core server ...
So off the bat you've already spend more than a month's rent for that studio in Sommerville your going to be camped out in ...
Whereas if you go the freebie Open Source route all you need to buy is hardware. Maybe your labour is more, but it's your blood, sweat, and tears which at an early point in the game is cheap. VS is a lot of .99c noodles! ;)
Yes the Java IDE's are somewhat inferior to MS's, but you can get everything you need to write, develop, manage, and host Java applications for free compared to MS; the OS, IDE, Web Server ... all cost money which can be a substantial amount for commercial purposes.