Licensing is, at least for a few years, a non-issue. You can join the Microsoft BizSpark program and get your fill of licenses. Take that off the table: The question is what is the toolset you can be most effective in quickly. You need to be able to create a product quickly, refine it in response to user input, and have this all leave you with enough time to market, network, and do all of the other things that it takes to be successful.
When you're successful you can even port it off to something else entirely or whatever. The key is that it doesn't sound like there's any reason for your customers to care what you wrote it in for you to deliver the value you want so do what's easiest for you. Now, if you're not the one that's going to be coding it the question is what is the easiest option for the people that will: Typically either friends you're already partnering with or whatever's widely available and affordable in your area.
I could go on, but the point is that Microsoft has a range of programs to keep their licensing very affordable (all but free) for startup companies. So pick based on what's going to get you in your situation to market fastest.