You're likely to find that this group is 90% against ASP.NET - at least, in the past, most .NET-related posts don't end well or contain too much positive info. Not to mention you're question seeks out a pretty specific person/group: those who have tried both in difficult situations.

There are other things to consider than just the language. I live in Dallas, Texas and Dallas has wonderful colleges but none of them are really tech-focused. As such, we tend to have no MSFT-trained developers coming out of the tech schools. So, what that means is that Dallas has a very good group of open source developers vs. a smaller group of .NET developers (at least that's been my experience in trying to hire). So, does your area have more of one type of developer? That might influence you as well. If your startup succeeds, you'll need more folks to help and it's easier to hire locally than for a startup to afford a relocation package.