Regarding the language doesn't matter thing I think that's mostly true. If you're choosing between Ruby and ASP.Net MVC I don't think you can loose. But sometimes the framework does matter, like if you want to build a startup on webforms (don't).
I think you're right about WebForms in the sense that I can't think of a single good reason to go with it over MVC. I maintain that it was never really intended for the web we use these days anyway.
It was designed to make web development "simple" for the kind of people who built WinForms applications and were too lazy to learn how the web actually works.
Thankfully Microsoft have learnt from their errors so are now pushing these types towards making a mess of Javascript. Visual Basic types will be happy to learn that semicolons are optional.