I think there are many things that you need to consider when deciding on a technology. One is preexisting skill, if you are already a .Net C# person then go with what you know. That being said rails is free and can be deployed on *nix which is also free.

Dont get caught up too much in worrying what other people are using. You initial technology stack will not make or break your company as you can always iterate to another technology stack at a later date if you wish.