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.
Wow, I live in Dallas and the .NET community is very large here (have you attended any of the .NET user group meetings?)
Honestly I find the OSS community to be very weak here since most developers are corporate type and they know either Java or C# or VB.NET. Every OSS (Python) meeting I've ever been to has been populated by back room tinkerers and people that "haven't done it" (tm) so they aren't any help to me with my real world questions and problems.
Now if you expect any college to put out good developers you have the wrong expectations for what college does. They are not Devry (which you should never hire a developer from Devry). Colleges teach theory not practice (which has been beaten like a dead horse on the net).
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.