Python+Tornado vs Scala+Lift?
I would suggest going with Python for these reasons:
1. Debugging
What I find especially useful when writing Python code, is the ability to easily debug ( see the pdb module ), all you need is a command prompt and a text editor to set your breakpoints. 
With Scala, you will probably have to rely on a IDE to do all your debugging.
2. Easy to learn
As for programming language, I don't know what your experiences with either languages are. If you are both Python and Scala beginners, my personal opinion is that you will learn Python faster.
I'm looking to start a Google Maps based web application. 
My initial thoughts are that in the first phase the focus should be on the front-end, and the backend should be easy to write and to prototype, and should aid as much as possible the development of the frontend.
There will be no 'classic' pages, just a meebo.com style interface. javascript + jquery. (meaning, very few if none at all static pages).
My eye has caught the comet-style , server push paradigm, and I'm really interested in doing some proof of concepts with this.
Do you have any recommendations or advantages and disadvantages or any experiences in working with :
Python + Tornado vs Scala + Lift ?
What other advantages or disadvantages in other areas of a web application might a choice bring?
Note : This is for max 2 developers, not a big distributed and changing team.
Thanks