We are a dev shop with a lot of experience with .NET. For our most recent web project we decided to take RoR for a spin. Things that would take an hour in .NET took us days. Not because RoR is lacking, but because we just don't have as deep a knowledge of Ruby or Rails.
Having used both, I can't think of a compelling technical reason to choose one over the other. I personally think .NET has a nicer tool chain, but RoR's tools are more than adequate.
If you do go with .NET and you are intending on forming a real company, then depending on which country you are in you can get pretty much all of the Microsoft development software for (I think) $100 - payable at the end of 3 years. I don't think this is open to every country, but a pretty cool programme to enrol in if you can. Microsoft Bizspark I think it is called. There are a few other variations as well, for different types of startups.
We are a dev shop with a lot of experience with .NET. For our most recent web project we decided to take RoR for a spin. Things that would take an hour in .NET took us days. Not because RoR is lacking, but because we just don't have as deep a knowledge of Ruby or Rails.
Having used both, I can't think of a compelling technical reason to choose one over the other. I personally think .NET has a nicer tool chain, but RoR's tools are more than adequate.
Go with what your developers want to use.