If you like more componentized approach with .NET power then ASP.NET is the way to go. Otherwise rails may suit you better. One practical thing a rail is better is that it can follow true bidirectional associations.
Pros of Ruby on Rails:
* Open Source and Community Driven
* Cross platform, works every where
* Extremely Scalable
* Built in unit testing and Ajax support
Cons of Ruby on Rails:
* No Unicode yet. You can over come this with JRuby on Rails and Iron Ruby on Rails
* Green threads. It doesn't use real os threads. Look above.
* The down side of the MVC pattern. You have to type a lot of html
* Most software shops don't know about it. So it is unlikely that you can use it at work.