Neither is very useful if you need to support many platforms. Microsoft it too entrenched in their walled garden mentality. Cross platform development never will be their strong side and it's their downfall.
MVC4 would be blocked by:
> MVC4 - Partial, no async features supported. > ASP.NET 4.5 Async Pipeline - Needs an parallel processing pipeline with async support, not done.
Still doesn't change the fact that these techs are one of the best ever made.