Any mainstream language you choose will be scalable enough.

Spend some time reading online rails and django documentation. Either one will be fine for you to learn.

My personal opinion is that Python is easier to learn for a beginner, but not by much. Ruby has http://hacketyhack.net/ which is a fun way to learn, and Python has http://www.diveintopython.org/ which is a tremendous (and free!) resource.

I say flip a coin and roll with it. They're both great languages and both frameworks are great for learning.

[Errr... The submission changed after my response was entered, sorry if it seems a bit off-topic.]