I'm a Python/Django developer myself so I'm pretty biased. I don't have anything against Ruby/RoR.
I'd take a look at the languages that the frameworks are built in and see which one you think you'd prefer.
I personally like how Python is structured so I went with Django. I know some fabulous programmers who prefer Ruby so they went with RoR. I personally wouldn't stick with PHP, but I know people who make a very descent living with it as well.
You can't really go wrong either way. but for now MVC is definitely the way to go. I'd look at the language first and the framework second.
Also, sometimes clients and/or the company you work for will make this decision for you. As long as you understand the underlying concepts of MVC and web development, it shouldn't be too much of a hassle to learn a new framework.