The perspective I've come away with is.....MVC is MVC. So far I haven't seen anything from any of these frameworks that is completely different when building a webapp (they're of course different when you're building different types of applications, such as Batch, Three Tier, etc).
I found myself worrying about the same things (Input Validation, internal state, database management, Object mapping to the database, and Output serialization) in each case. The optimal choices depended heavily on the characteristics of the input domain and the problem domain.
Meaning, for a simple CRUD app, I'd probably use Rails (mainly for their scaffolding), for something that was more event based (like transactions/financial), I'd probably use Java/Spring, for something that was more system level or batch, I'd probably use C/C++ or Perl depending on how numerical/stringy the data is. I'd probably use PHP if I didn't want a bunch of startup time (i.e. if I just wanted to prototype something really quickly), ASP.NET if it was going to be Windows.
After picking up a couple of these, I stopped thinking about the solution in terms of the language, but more in terms of the Paradigm.
Sorry I couldn't be of more help