If you are a Microsoft shop either way then it doesn't matter too much, but if you're making technological choices now, consider how well that will scale without free licenses (e.g. ASP.net/MVC, how much is Windows Serve licensing going to cost you? Visual Studio? Active Directory? MS SQL?).
This isn't an anti-Microsoft post, just a post to remind everyone to think about the future of your small business with technological choices. Bizspark is designed for you to get yourself into the Microsoft's way of doing things (which is good and bad, depending on your needs, etc).
I actually like Microsoft's stack, but realise it is expensive, too expensive for many small businesses.